Detection and Dynamics of Exoplanets (DDE): Interplay between theory and observations

7 Jul 2025, 00:30 → 11 Jul 2025, 22:00 Europe/Lisbon

Auditorium C.1 (Physics Department, University of Coimbra)

Welcome to the DDE

Detecting and characterizing planets in multiple systems is not an easy task, because the traces of each body overlap, and the observations can be reproduced by different orbital configurations. Additionally, in many systems, planets are involved in mean motion resonances or resonant chains, making it even more difficult to disentangle the individual contributions. In the DDE meeting, we aim to bring together communities of observers and theoreticians working on exoplanets. Through the exchange of knowledge and difficulties, we hope that it will be possible to develop common strategies to extract the maximum constraints from observational data and theoretical models.

ARTICLE TOPICAL COLLECTION

We invite all participants in the DDE meeting to submit high-quality original contributions to the special issue "Detection and Dynamics of Exoplanets (DDE): Interplay between theory and observations" on Celestial Mechanics and Dynamical Astronomy journal. These contributions are regular peer-reviewed articles that should address problems related to the detection, dynamics, or characterization of planets in multiple systems.

KEY TOPICS

- Astrometry and direct imaging
- Exomoons, exorings, and trojan systems
- Formation and evolution of planetary systems
- Planets in binary systems
- RV-detected multiple systems
- Stability and dynamics of planetary systems
- Star-planet interactions and exoplanets' characterization
- Synergies between theory and observations
- TTVs and transit-detected compact systems

KEY SPEAKERS

- Susana Barros (IA, University of Porto, Portugal)
- David Kipping (Columbia University, USA)
- Anne-Marie Lagrange (Paris Observatory, France)
- Adrien Leleu (University of Geneva, Switzerland)
- Cristobal Petrovich (Indiana University Bloomington, USA)
- Hilke Schlichting (University of California, Los Angeles, USA)
- Amaury Triaud (University of Birmingham, UK)
- Stéphane Udry (University of Geneva, Switzerland)

SCIENTIFIC ORGANIZING COMMITTEE

- Alexandre Correia (chair, University of Coimbra, Portugal)
- Anne-Sophie Libert (co-chair, University of Namur, Belgium)
- Nuno Santos (co-chair, IA, University of Porto, Portugal)
- Rodrigo Diaz (University of San Martin, Argentina)
- Jacques Laskar (Paris Observatory, France)
- Monika Lendl (University of Geneva, Switzerland)
- Jack Lissauer (NASA Ames Research Center, USA)
- Rosemary Mardling (Monash University, Australia)
- Helena Morais (São Paulo State University, Brazil)

LOCAL ORGANIZING COMMITTEE

- Alexandre Correia (chair)
- Anne-Sophie Libert (co-chair)
- Nuno Santos (co-chair)
- Sonia Antón
- Isabel Melo
- João Rosa
- Rodrigo Silva
- Timothée Vaillant
- Konstantinos Zafeiropoulos

IMPORTANT INFORMATION / DATES

– December 1st, 2024: Registration Opens
– March 31st, 2025: Registration Deadline*
– May 8th, 2025: Program Release

*There is a limit of 120 participants, Registration will close as soon as this number is reached.

DDE_poster.pdf

Monday 7 July

Registration

Opening Session

RV-detected multiple systems

The radial-velocity technique was the first to reveal an exoplanet and it is the second most successful one. It is particularly sensitive to large mass planets, which trigger more disruptive gravitational interactions in the system. It is also not limited to planets in the line-of-sight (like the transit technique). Therefore, some of the most unexpected dynamical configurations were found with this technique (e.g., planets with high mutual inclinations or planets in compact binaries). By correctly modeling the planet-planet interactions, we can extract the complete dynamical configuration of the orbits (e.g., retrograde planets) and their true masses.

1 Decades long planet search surveys around solar type and giant stars. A multi planet view

TBD

Speaker: Stéphane Udry (University of Geneva)

2 HD 110067 Resonant Chain: Evidence for Quiescent Formation from Multi-Planet Spin-Orbit Measurements

Multiplanetary systems in resonance offer a unique insights into planet formation and evolution. While resonant configurations, particularly among sub-Neptunes, probe dynamical and atmospheric interplay, their origins and survival rates remain debated. Theoretical models suggest primordial misalignment could disrupt resonance during formation; consequently, surviving resonant systems are predicted to exhibit lower spin-orbit angles compared to their non-resonant counterparts, indicative of less disruptive histories. The Rossiter-McLaughlin effect allows us to determine the spin-orbit angle as this parameter is indicative of formation and evolutionary pathways of exoplanetary systems. In this talk, I will show multi-facility observations of HD 110067, resonant chain of six sub-Neptunes orbiting a star in a triple system. The orbits of the second inner-most planet HD 110067c as well as the outer planet HD 110067g are well aligned. This is the first time the spin-orbit angles of more than a single planet have been measured for a pristine resonant chain. This result is indicative that the current architecture of the system has been reached through convergent migration without any major disruptive events. The RM effect also aids in constraining TTVs of these small planets unraveling why resonant systems display overall lower densities compared to non-resonant ones.

Speaker: Jiri Zak (Astronomical Institute of Czech Academy of Sciences)

3 An updated view on the infant multi-planetary system V1298 Tau through dedicated spectroscopic, photometric, and radio follow-up campaigns

V1298 Tau is a very young (20 ± 10 Myr) multi-planetary system that represents a benchmark laboratory for studying the early stages of planets' formation and evolution. Mainly due to the high levels of stellar magnetic activity, an undisputed description of the system has remained elusive so far, including the measurements of the planetary masses and densities, and the characterisation of its orbital architecture. With the aim of shedding light on this enigmatic system, we will present preliminary results from intensive spectroscopic and photometric follow-up campaigns, through which we collected almost 400 radial velocity measurements with HARPS-N@TNG, and several additional ground- and space-based transits of the four confirmed planets. These new data and results are expected to provide a significant contribution towards the understanding of the formation and dynamical evolution pathways of V1298 Tau in the first few Myrs, making this a benchmark system among the still limited sample of infant exoplanets detected so far. Additionally, we will report on the first detection of variable radio emission from V1298 Tau, which contributes to the understanding of the stellar magnetic activity properties, and the impact on planetary evolution at the early stages.

Speaker: Mario Damasso (INAF-Astrophysical Observatory of Torino)

10:30 coffee-break

RV-detected multiple systems

The radial-velocity technique was the first to reveal an exoplanet and it is the second most successful one. It is particularly sensitive to large mass planets, which trigger more disruptive gravitational interactions in the system. It is also not limited to planets in the line-of-sight (like the transit technique). Therefore, some of the most unexpected dynamical configurations were found with this technique (e.g., planets with high mutual inclinations or planets in compact binaries). By correctly modeling the planet-planet interactions, we can extract the complete dynamical configuration of the orbits (e.g., retrograde planets) and their true masses.

4 The strongly interacting planetary system WASP-148

WASP-148 is an extrasolar system including two giant planets near the 4:1 mean-motion resonance. The inner one was first identified as a transiting candidate on a 8.8-d period from the SuperWASP photometric survey, then the SOPHIE spectrograph allowed it to be characterized, as well as the outer (P = 34.5 days) planet to be detected. Among other effects, the mutual gravitational interactions between both planets cause transit-timing variations of a few minutes, which were detected with ground-based photometry, including by volunteers. This made WASP-148 one of the few cases where such a phenomenon is seen without space-based photometry. Subsequent TESS observations confirmed and refined those results. Different hypotheses were adopted to analyse the data and measure the system's parameters, constrain its stability and its future evolution. They allow interesting comparisons between technics. They indicate in particular a significant mutual inclination of both planetary orbital planes, making WASP-148 a rare case of non-coplanar planetary system. Still, the presence of a possible third, outer planet in the system would affect that inclination.

Speaker: Guillaume Hébrard (Institut d'Astrophysique de Paris)

5 Efficient stability constraints in RV detection limits with ARDENT

Super-Earths and sub-Neptunes are the most abundant type of planets in the Galaxy, and yet, they are absent from the Solar System. A possible reason for this absence is the giant planets. Indeed, their gravitational influence could have prevented the inward migration of enough disc material needed to form super-Earths. Dedicated RV surveys investigate this hypothesis, by searching for inner small planets in systems that harbor a giant, and vice-versa. As of today, there is no consensus about a (anti-)correlation between inner super-Earths/sub-Neptunes and the presence of outer giant planets. As observational efforts continue, the computation of reliable detection limits is essential to draw rigorous conclusions. They are key to better understand the systems’ architecture and to tailor specific RV follow-ups. However, those detection limits do not take into account the gravitational interactions between the known planets and the hypothetically hidden one. These interactions can lead to strong orbital instability, further discarding entire regions of the mass-period parameter space. In this presentation, I will introduce ARDENT, an open-source Python code for the fast and efficient computation of dynamical detection limits (i.e. detection limits that include the stability constraints). We combined both analytical and numerical stability criteria to balance computation time and reliability. We also optimized the parameter space exploration to further decrease execution time. I will present a few applications of ARDENT, emphasizing the improvement that stability criteria bring on the detection limits.

Speaker: Manu Stalport (University of Liège)

6 Characterization of seven transiting systems, including four warm Jupiters from SOPHIE and TESS

While several thousand exoplanets are now confirmed, the number of known transiting warm Jupiters ($10 ~\text{d} < \text{period} < 200 ~ \text{d}$) remains relatively small. These planets are generally believed to have formed outside the snowline and migrated to their current orbits. Because they are sufficiently distant from their host stars, they mitigate proximity effects and so offer valuable insights into planet formation and evolution. In this talk, we present the study of seven systems, three of which -- TOI-2295, TOI-2537, and TOI-5110 -- are newly discovered planetary systems. Through the analysis of TESS photometry, SOPHIE radial velocities (RVs), and high-spatial resolution imaging, we found that TOI-2295b, TOI-2537b, and TOI-5110b are transiting warm Jupiters with orbital periods ranging from 30 to 94 d, masses between 0.9 and 2.9 $M_{\rm{J}}$, and radii ranging from 1.0 to 1.5 $R_{\rm{J}}$. Both TOI-2295 and TOI-2537 harbor at least one additional, outer planet. Their outer planets -- TOI-2295c and TOI-2537c -- are characterized by orbital periods of 966.5$^{+4.3}_{-4.2}$ and 1920$^{+230}_{-140}$ d, respectively, and minimum masses of 5.61$^{+0.23}_{-0.24}$ and 7.23$^{+0.52}_{-0.45}$ $M_{\rm{J}}$, respectively. We have also investigated and characterized the two recently reported warm Jupiters TOI-1836b and TOI-5076b, which we independently detected in SOPHIE RVs. Our new data allow for further discussion of their nature and refinement of their parameters. Additionally, we study the planetary candidates TOI-4081.01 and TOI-4168.01. For TOI-4081.01, despite our detection in RVs, we cannot rule out perturbation by a blended eclipsing binary, and we thus exercise caution regarding its planetary nature. On the other hand, we identify TOI-4168.01 as a firm false positive; its RV curve exhibits a large amplitude in an antiphase relation with the transit ephemeris observed by TESS, indicating that the detected event is the eclipse of a secondary star rather than a planetary transit. Finally, we highlight interesting characteristics of these new planetary systems. The transits of TOI-2295b are highly grazing, with an impact parameter of 1.056$^{+0.063}_{-0.043}$. This leaves its radius uncertain but potentially makes it an interesting probe of gravitational dynamics in its two-planet system, as transit shapes for grazing planets are highly sensitive to even small variations in inclination. TOI-2537b, in turn, is a temperate Jupiter with an effective temperature of 307$\pm$15 K and can serve as a valuable low-irradiation control for models of hot Jupiter inflation anomalies. We also detected significant transit timing variations (TTVs) for TOI-2537b, which are likely caused by gravitational interactions with the outer planet TOI-2537c. Further transit observations are needed to refine the analysis of these TTVs and enhance our understanding of the system’s dynamics. Finally, TOI-5110b stands out due to its orbital eccentricity of 0.745$^{+0.030}_{-0.027}$, one of the highest planetary eccentricities discovered thus far. We find no conclusive evidence for an external companion, but an unseen planet with a semi-amplitude smaller than 10 m/s could nonetheless still be exciting its eccentricity.

Speaker: Neda Heidari (Institut Astrophysique Paris)

7 Unveiling transiting temperate giants in multi-planetary systems

Most detected transiting planets have orbits of a few tens of days, exposing them to intense stellar irradiation and interactions that significantly alter their properties. In contrast, colder planets with longer orbital periods are less affected, offering crucial insights into their formation and migration histories. In this talk, I report the detection and characterization of two multi-planetary systems hosting a transiting temperate Jupiter with an orbital period larger than 100 days and an inner non-transiting planet, thanks to a four-year ground and space-based photometric and radial velocity survey. Combining precise masses, radii, and ages with a state-of-the-art planetary evolution model, I infer the metal enrichment of the newly discovered temperate giants and explore their influence on the mass-metallicity correlation of giant planets.

Speaker: Solène Ulmer-Moll (Leiden University)

8 Dynamic masses of rocky planets in near-by planetary systems

The nearest rocky exoplanets are non-transiting, making their atmospheric characterization possible only through a combination of high spatial and spectroscopic separation of planetary and stellar light. Nearby rocky planets, particularly those in the habitable zone of their host stars, are prime targets for future missions such as LIFE and HWO to search for biosignatures. Most nearby stars are M dwarfs, meaning that the closest rocky planets are often found orbiting these low-mass stars. To prepare for future atmospheric studies, we have initiated efforts to determine the true masses of these planets by analyzing radial velocity variations caused by planet-planet interactions, using subtle deviations from Keplerian orbits. Long observational baselines combined with new high-precision, dense RV monitoring now enable the detection of dynamical effects in the sub-m-per-second range. Focusing on multi-planet systems around nearby M dwarfs, we present initial results that refine target selection and prepare for the next generation of exoplanetary exploration.

Speaker: Stefan Dreizler (University Goettingen)

9 Multiplanet systems from the ​Dispersed Matter Planet Project

Multiplanet systems in the exoplanet catalogues appear to be less well represented than Kepler transit statistics would suggest. Identification of exoplanet periodicities in radial velocity data via the sequential addition of Keplerian signals may lead to systematically biased multiplanet solutions. A Bayesian approach instead allows us to determine the optimal number of planet candidates by simultaneously fitting multiple signals. This is particularly important when several exoplanets are indicated in limited datasets as it enables competing solutions to be more completely assessed. I will present results from the Dispersed Matter Planet Project, which pre-identifies potential exoplanet systems through atmospheric mass loss that is imprinted on their host stars. Subsequent radial velocities on the systems we have identified have efficiently led to a number of diverse, predominantly low mass multiplanet systems where a Bayesian approach is crucial for optimal recovery of periodicities. I will examine the sensitivity of our survey to date and will discuss our targets in the context of the wider population of short period hot planets.

Speaker: John Barnes (The Open University)

12:30 lunch

Formation and evolution of planetary systems

By better understanding how a planetary system was formed and evolved into the currently observed configuration, we can put constraints on the planetary composition and initial planetary disk. We can also determine if the climates of the planets in the habitable zone can be stable over billions of years such that life can develop.

10 TBD

TBD

Speaker: Hilke Schlichting (University of California, Los Angeles)

11 From the Desert into the Savanna: a trek across the exo-Neptunian landscape

Close-in exoplanets are shaped by complex atmospheric and dynamical processes, to which exo-Neptunes appear to be particularly sensitive. While atmospheric erosion played a major role in forming the Neptunian "Desert" (a dearth of hot Neptunes at short orbital periods), it is not clear how far into the "Savanna" (a milder deficit of warm Neptunes at longer periods) this process is active and when in a planet life it occurs. Determining the fraction of planets brought close-in by early disk-driven or late high-eccentricity migration is thus essential to understand their overall evolution. This is the main goal of ATREIDES, a large collaboration bringing together observers and theoreticians experts in stars, planets, and their atmospheric and dynamical evolution, to exploit high-resolution transit spectroscopy and photometry of more than 60 close-in Neptunes. I will present the orbital architectures derived from the homogeneous analysis of Rossiter-McLaughlin signals measured with the VLT/ESPRESSO, and how their interpretation using secular evolutionary simulations brings constraints of the origins of the Neptunian "Ridge", an overdensity of planets recently found to separate the Desert and Savanna.

Speaker: Vincent Bourrier (Geneva Observatory)

12 Accelerating Planet Formation Simulations with Emulators

​Traditionally, characterizing the effects of different processes in planet formation has relied on performing large ensembles of simulations with slightly different initial conditions. The computational cost of planet formation simulations presents a barrier to exploring a multi-dimensional space of model parameters​, characterizing the precise predictions of planet formation models, ​and performing inference on ​observed exoplanet populations​.​ Recent progress in building emulators for complex physical models offers the hope of approximating the predictions of planet formation models at greatly reduced computational cost. When constructing an emulator, there are multiple design choices to be made, such as which parameters to use as input, which outputs to emulate, and whether to emulate specific steps of the model or only the final predictions. I'll describe recent progress in applying machine learning and emulation to planet formation models.

Speaker: Eric Ford (Penn State)

13 Mapping the exo-Neptunian landscape. A ridge between the desert and savanna

Atmospheric and dynamical processes are thought to play a major role in shaping the distribution of close-in exoplanets. A striking feature of such distribution is the Neptunian desert, a dearth of Neptunes on the shortest-period orbits. We aimed to define the boundaries of the Neptunian desert and study its transition into the savanna, a moderately populated region at larger orbital distances. To do so, we built a sample of planets and candidates based on the Kepler DR25 catalogue and weighed it according to the transit and detection probabilities. We then used the corrected distribution to study occurrences across the period and period-radius spaces. We delimited the Neptunian desert as the close-in region of the period-radius space with no planets at a 3σ level, and identified an overdensity of planets separating the Neptunian desert from the savanna (3.2 days ⪅ Porb ⪅ 5.7 days), which we propose to call the Neptunian ridge. The period range of the ridge matches that of the well-known hot Jupiter pileup (≃3–5 days), which suggests that similar evolutionary processes might act on both populations. Our revised landscape supports a previous hypothesis that a fraction of Neptunes were brought to the edge of the desert (i.e. the newly identified ridge) through high-eccentricity tidal migration (HEM) late in their life, surviving the evaporation that eroded Neptunes having arrived earlier in the desert. The ridge thus appears as a true physical feature illustrating the interplay between photoevaporation and HEM, providing further evidence of their role in shaping the distribution of close-in Neptunes.

Speaker: Amadeo Castro-González (Center for Astrobiology (CAB, INTA-CSIC))

14 Terrestrial planet formation considering various binary star configurations

To date there have been already 724 binary star systems discovered, which inhabit at least one planet. Most studies that have investigated the late stage of terrestrial planet formation in binary stars considered planar configurations, which might be accurate for tight binary stars. However, for wide binary stars it is assumed, that the inclination between the two stars is randomly distributed. Thus, a possible misalignment between the planet forming disk and the secondary star has to be taken into account. We investigate the evolution of a planetesimal-planetary embryos disks, consisting of 2000 planetesimals and 25 planetary embryos, in different misaligned binary star configurations. In the late stage of terrestrial planet formation (after the gas phase), the gravitational interactions of the disk objects dominate. To study all the gravitational interactions in a reasonable time, we apply our GPU parallelized N-body code GANBISS and compute the dynamical evolution of the disks, where the planetary embryos grow to terrstrial-like planets via perfect inelastic collisions. As collisions among planetary embryos and planetesimals have in reality a more diverse outcome, we perform post-processing analysis of all collisions that occur during the N-body simulations, by making use of an analytic model. Our full N-body approach of embryo-planetesimal disks indicate mainly two results in the dynamical evolution of the disk: (i) In misaligned configurations planetary embryos undergo an inward migration due to dynamical friction and collisions, leaving space in the outer part of the disk for an asteroid-belt like structure. (ii) The planetary embryos align onto the inclination of the secondary with small variations due to dynamical friction and collisions, except in highly inclined configurations (inclination of the secondary $i_b = 45^\circ$) in the outer regions of the disk, where the variations of the inclination of the embryos are larger. Comparing the collision outcomes between planar and inclined configurations, we find a strong increase of the destructive collisions, especially for planetesimal-planetesimal collisions in inclined binary stars.

Speaker: Max Zimmermann (TU Graz)

15 A New and Advanced Approach to the Formation and Composition of Terrestrial Planets

We present the results of a new and comprehensive approach to simulating the formation of terrestrial planets. Our approach begins with simulating the collisional growth of the first planetesimals and continues with resolving giant impacts using our state-of-the-art SPH-based model. We take into account all relevant physical processes including the dynamical friction due to the debris and planetesimal disks, migration of planetesimals and embryos, and the perturbation as well as possible migration of giant planets. Also, for the first time, we consider a more realistic protoplanetary disk where the distribution of planetesimals and planetary embryos are not approximated by a mathematical function, but instead contain depletions and inhomogeneities. Results point to several important findings. In the context of our solar system, almost all simulations produced an Earth-analog. Also, Mars-analogs appeared routinely in regions with local density depletions where the disk lacked material. These results seem to imply that the formation of Earth could have been due to the natural dynamical evolution of the protoplanetary disk and the small mass of Mars seem to be due to the non-uniform distribution of the disk material. Simulations also show that the capture into resonance of migrating giant planets does not play a significant role on the formation of rocky planets. Super-Earths are formed routinely when giant planets migrate. In regard to the composition of terrestrial planets, our results suggest that while giant planets may affect the inventory of planet-forming material, they play no role in the mechanics of the formation of rocky planets and the transfer/transport of chemical compounds to them. Formation and delivery of chemical compounds are merely due to the mutual interactions of planetary embryos, a process that occurs even when no giant planet exists. We will present the results of our study and discuss their applications to the formation and composition of terrestrial planets in our solar system and extrasolar planets.

Speaker: Nader Haghighipour (PSI & IfA Hawaii)

16 Unveiling the Nature of Close-In Neptune Planets: Insights from a Homogeneous Planetary Sample

Using a homogeneous analysis approach, we present a comprehensive study of close-in Neptune-sized planets. We compile a well-defined sample of TESS-observed planets, ranked based on their orbital period, radius, and the visual magnitude of their host stars. To ensure precise radial velocity measurements, we incorporate archival and new HARPS data, resulting in a final sample of 64 targets—46 confirmed planets and 18 with no significant radial velocity signals. Our analysis explores key planetary and stellar properties, including the mass-radius distribution, planetary density, host star metallicity, and the presence of stellar and planetary companions. Notably, we find that 26% of our sample belongs to multi-planet systems, primarily located near the lower boundary of the Neptunian desert. Focusing on a subset of 33 confirmed planets with radii between 2𝑅⊕ and 10𝑅⊕, we calculate envelope mass fractions (EMFs) using the GAS gianT modeL for Interiors (GASTLI). Our results reveal a striking division in EMFs based on equilibrium temperature: planets with temperatures above 1300 K (or orbital periods shorter than ~3.5 days) exhibit near-zero EMFs, while those beyond this threshold typically have EMFs between 20% and 40%, scaling linearly with planetary mass. Intriguingly, this orbital period boundary aligns with the transition from the Neptunian desert to the recently identified Neptunian ridge, suggesting distinct formation or evolutionary processes at play. These findings provide new insights into the nature of close-in Neptune-sized planets and their atmospheric evolution, offering a fresh perspective on the underlying mechanisms shaping their distribution.

Speaker: Lauren Doyle (University of Warwick)

16:00 coffee-break

Formation and evolution of planetary systems

By better understanding how a planetary system was formed and evolved into the currently observed configuration, we can put constraints on the planetary composition and initial planetary disk. We can also determine if the climates of the planets in the habitable zone can be stable over billions of years such that life can develop.

17 The formation of the TRAPPIST-1 system in two steps during the recession of the disk inner edge

TRAPPIST-1 hosts seven planets. The period ratios of neighbouring pairs are close to the 8:5, 5:3, 3:2, 3:2, 4:3 and 3:2 ratios in increasing distance from the star. The Laplace angles associated with neighbouring triplets are observed to be librating, proving the resonant nature of the system. This compact, resonant configuration is a manifest sign of disk-driven migration; however, the preferred outcome of such evolution is the establishment of first-order resonances, not the high-order resonances observed in the inner system. Here, we explain the observed orbital configuration with a model that is largely independent of the specific disk migration and orbital circularization efficiencies. Together with migration, the two key elements of our model are that the inner border of the protoplanetary disk receded with time and that the system was initially separated into two subsystems. Specifically, the inner b, c, d and e planets were initially placed in a 3:2 resonance chain and then evolved to the 8:5-5:3 commensurability between planets b, c and d due to the recession of the inner edge of the disk, whereas the outer planets migrated to the inner edge at a later time and established the remaining resonances. Our results pivot on the dynamical role of the presently unobservable recession of the inner edge of protoplanetary disks. They also reveal the role of recurring phases of convergent migration followed by resonant repulsion with associated orbital circularization when resonant chains interact with migration barriers.

Speaker: Gabriele Pichierri (Università degli Studi di Milano)

18 Equilibria in resonant chains

Planetary systems in resonant chains are of particular interest both from a dynamical point of view and an observational point of view. In particular the three planet resonant angles are a valuable observable for transiting systems. Indeed, transit timing observations allow to measure the libration of these angles while in most cases the two planet angles cannot be observed. The final equilibrium of three planet angles (around which the system is observed to librate) depends on the formation and evolution of the system. Models of resonant chains can also be used (and have been used) to predict the periods and phases of additional planets in systems known to already harbor resonant planets. In this talk, I will present an analytical model of resonant chains and its application to several observed systems.

Speaker: Jean-Baptiste Delisle (University of Geneva)

19 Formation of Hot Jupiters in Systems with Too-Distant Binary Companions

The formation of hot Jupiters remains an open question, with many proposed mechanisms well-suited to explain subsets of the observed population. Notably, the traditional high-eccentricity migration mechanism driven by a distant stellar companion is one of the oldest hot Jupiter formation channels, and it is often cited as the formation mechanism for hot Jupiters on high-obliquity orbits. However, many hot Jupiter systems lack suitably-close binary companions for high-eccentricity migration. I will discuss a new mechanism for driving hot Jupiter formation in systems with wide binary companions involving an intermediate body and discuss a tentative detection of such a system where this mechanism may operate.

Speaker: Yubo Su (Princeton University)

20 Identifying hot Jupiters that arrived via disk migration

Two leading hypotheses of hot Jupiter formation are disk migration, where a Jupiter in the outer part of the disk and migrates inward due to gas drag, and high eccentricity migration (HEM), where a Jupiter is excited to an eccentric orbit by its stellar or planetary companion and subsequently circularizes close to the pericenter distance due to tidal dissipation in the planet. Measurement of stellar obliquity, a byproduct of the eccentricity excitation, has been a common method of testing the two hypotheses, but while a high obliquity suggests HEM, low obliquity does not necessarily suggest disk migration. This is because obliquity could damp due to tidal dissipation in the star, and hot Jupiters that arrived via HEM could very well have aligned orbits as well. In this study, we therefore attempt to identify hot Jupiters that may have arrived by disk migration by calculating τcirc, the circularization timescale of about 400 hot Jupiters with measured masses and radii. For systems where τcirc > τage (estimated age of the system) but the eccentricity e = 0, HEM would not be able to complete in time, suggesting disk migration. Tidal quality factor used to calculate τcirc was determined as the value that maximizes the difference between the eccentricity distributions of the two samples with τcirc > τage and τcirc < τage. Tidal quality factor obtained are consistent with the values for Jupiter in the solar system estimated from the interactions with the satellites. As a result, we identified dozens of hot Jupiters (τcirc > τage, e = 0) that are suggestive of disk migration. While the list includes many of the hot Jupiters with known inner companions (also hinting disk migration), it does not include ones on significantly inclined orbits. This is consistent with disk migration being a more quiescent migration mechanism than HEM. We also report that the accuracy of the estimation of the tidal quality faactor (p-value of the difference in the eccentricity distribution) deteriorated significantly when hot Jupiter for which e was assumed to be zero (but not measured) were included. This suggests that many of these hot Jupiter have significant eccentricities.

Speaker: Yugo Kawai (The University of Tokyo)

21 THIRSTEE: testing the water world hypothesis on the small transiting exoplanet population

The sub-Neptune population currently poses a conundrum. Are the smallest sub-Neptunes "gas dwarfs" (Earth-like cores surrounded by H/He envelopes) or "water worlds" (planets composed of ice and rock that migrated inward after forming beyond the snow line)? And if both populations exist, what are their distinguishing properties, and how do they depend on stellar type? Recent studies propose that for M dwarfs, the observed radius valley in the sub-Neptune population could stem from compositional differences (supporting the water-world hypothesis) instead of atmospheric mass loss. A similar result for FGK stars would reshape our interpretation of planet demographics, and influence formation and evolution theories, but testing this requires a larger sample of well-characterized exoplanets across diverse stellar types. The dependence on planet bulk density with host spectral type contains the most information to connect the observed population with global models of planet formation and evolution. On the other hand, a sample of sub-Neptunes with ranging equilibrium temperatures and host spectral types is necessary to constrain the chemistry and interior structure of this population via atmospheric characterisation.The THIRSTEE program aims at investigating the origin and nature of sub-Neptunes by collecting extremely precise radial velocity data for small transiting planets using ultra-precise spectrographs to : 1) expand the sample of small planets around M dwarfs, and 2) refine mass estimates of seemingly intermediate water mass fraction planets around FGK stars. I will present the program’s design and initial results, focusing on four newly-characterized M-dwarf systems. Our early findings suggest that most THIRSTEE-observed systems align with a water-world or Earth-like population.

Speaker: Gaia Lacedelli (IAC - Instituto de Astrofísica de Canarias)

22 Characterisation of young multi-planetary systems with CHEOPS

One of the primary and long-standing goals of the planetary science community is to understand planet formation and evolution. Most studies so far have been limited to planets around fully evolved stars, including those in the Solar System. However, models predict that the major phases of planetary evolution—such as formation (<3 Myr), disk migration (<5 Myr), evolutionary cooling (3–400 Myr), and dynamical migration (100–1000 Myr)—occur within the first billion years after formation. Planetary evolution is fastest in the early stages of formation and it is also the phase where differences in the model predictions are visible. Accurate and precise characterization of young exoplanets provides a crucial pathway for testing planet formation and evolution models. However, the young stars hosting these planets are often magnetically active, leading to stellar surface inhomogeneities such as spots and plages, which hinder accurate characterization. Multiple studies have found a prevalence of resonant configurations in young planetary systems (Dai et al. 2024, Hamer et al. 2024). This provides an opportunity to constrain planetary masses and measure bulk densities, enabling studies of planetary composition and interior structure—both of which are vital for understanding planet formation and evolution. In this talk, I will present our work on two young, resonant, multi-planetary systems—HIP 67522 (17 Myr) and TOI-942 (<100 Myr)—using high-precision photometry from the CHEOPS satellite. CHEOPS' higher sensitivity at blue wavelengths allows us to better constrain activity-induced biases in inferred planet properties, including transit timings and depth. For HIP 67522, we observe transit depth variations of up to 30% between individual observations. These variations evidently correlate with the star's rotational variability signal, pointing to varying spot coverage as their cause. For TOI-942, we identified transit timing variations with an amplitude of approximately 20 minutes, enabling us to dynamically measure planetary masses.

Speaker: Hritam Chakraborty (University of Geneva)

23 Planetary Edge Trends (PET). I. The Inner Edge-Stellar Mass Correlation

Recent advancements in exoplanet detection have led to over 5,700 confirmed detections. The planetary systems hosting these exoplanets exhibit remarkable diversity. The position of the innermost planet (i.e., the inner edge) in a planetary system provides important information about the relationship of the entire system to its host star properties, offering potentially valuable insights into planetary formation and evolution processes. In this work, based on the Kepler Data Release 25 (DR25) catalog combined with LAMOST and Gaia data, we investigate the correlation between stellar mass and the inner edge position across different populations of small planets in multi-planetary systems, such as super-Earths and sub-Neptunes. By correcting for the influence of stellar metallicity and analyzing the impact of observational selection effects, we confirm the trend that as stellar mass increases, the position of the inner edge shifts outward. Our results reveal a stronger correlation between the inner edge and stellar mass with a power-law index of 0.6-1.1, which is larger compared to previous studies. The stronger correlation in our findings is primarily attributed to two factors: first, the metallicity correction applied in this work enhances the correlation; second, the previous use of occurrence rates to trace the inner edge weakens the observed correlation. Through comparison between observed statistical results and current theoretical models, we find that the pre-main-sequence (PMS) dust sublimation radius of the protoplanetary disk best matches the observed inner edge-stellar mass. Therefore, we conclude that the inner dust disk likely limits the innermost orbits of small planets, contrasting with the inner edges of hot Jupiters, which are associated with the magnetospheres of gas disks, as suggested by previous studies. This highlights that the inner edges of different planetary populations are likely regulated by distinct mechanisms.

Speaker: Mengfei Sun (Nanjing University)

Tuesday 8 July

Exomoons, exorings, and trojan systems

Most solar system planets have moons and rings and so we also expect them to exist around exoplanets. Co-orbital bodies (trojan) are also abundant around Jupiter and Neptune. With the current observational technology, we are at the limit of detecting these bodies and structures. Dynamical studies can tell us which planetary systems are the most favorable to look for them.

24 Exomoons, exorings, and other exotica

Since the first exoplanets were found, astronomers have speculated about the possibility of detecting other minor bodies and effects associated with these worlds. Each of these promises to unlock new insights into exoplanets which would be otherwise inaccessible, such as their obliquity, internal structure and details of their history and evolution. In this talk, I will summarise what progress has been made in the search for a myriad of such effects, in particular exomoons, exorings, trojans and planetary oblateness. Each poses unique detection challenges but in the JWST-era I argue they should certainly be at last detectable. Exomoons has enjoyed perhaps the greatest attention in the literature, with dozens of methods now proposed for their detection, and candidates announced too. Arguably the greatest issue facing this emerging field is the lack of a truly convincing detection, which would likely need to be a moon akin to those found in the Solar System to gain widespread acceptance. Exorings have long been sought after, but are often overlooked. I highlight how most modern precision light curve detrending methods would remove ring signatures by design, and planets with large projects ring areas could even be classified as false-positives. Trojans, like moons, have been sought using statistical stacking approaches, as well as individual searches, but I highlight the precarious nature of the former approach. Finally, planetary oblateness offers perhaps the most promising and likely exotica to expect near-term detections, with candidate detections already in the literature and with the potential to unlock planet-orbit obliquity measurements.

Speaker: David Kipping (Columbia University)

25 Looking closer at PDS 70: tracing trojan dust?

The PDS 70 system hosts the only two non-controversial protoplanets, offering a unique laboratory for planet formation studies. For instance, ALMA revealed around PDS 70 c the only circumplanetary disk ever detected. Also using ALMA data, we tentatively detected a trojan dust cloud sharing orbit with PDS 70 b. Remarkably, several authors have reported evidence for the presence of an additional inner source using different instrumentation, including VLT/SPHERE and JWST/NIRCam. While its apparent Keplerian motion has led to its classification as candidate planet d, its spectrum casts doubt on its true nature. In this talk, we will present new and deeper follow-up VLT/SPHERE observations providing new insights on the candidate, and raising alternative hypotheses that will be presented in this talk.

Speaker: Olga Balsalobre-Ruza (Centro de Astrobiología (CAB))

26 Large transiting exoring systems from the ASAS-SN survey

Wide field surveys searching for transiting exoplanets also record and discover both known stellar variability and previously unknown phenomena. Deep and complex eclipses of otherwise unremarkable stars reveal eclipsing companions that have complex substructures. The ASAS-SN survey has now produced over a dozen complex eclipses that last from weeks to years, and we present our analyses of several of these light curves, including a multi-year ringed disk transit and more recently two eclipses that are indicative of ringed disks. Future wide and deep time domain surveys, such as the Vera C. Rubin Observatory and the upcoming release of Gaia DR4, will considerably increase the number of these objects.

Speaker: Matthew Kenworthy (Leiden Observatory)

27 Astrometric exomoon detection with VLTI/GRAVITY+ and future facilities

With the publication of Gaia DR4, astrometry will mature from a future prospect to a highly prosperous and efficient method of exoplanet detection. Monitoring the slight orbital wobbles that potential host stars show over long periods of time will reveal the presence of thousands such planets. It is now the time to prepare for taking the astrometric detection method to the next level: for the first time, the novel possibilities offered by the emergent field of NIR interferometry, more precisely the unprecedented astrometric accuracy and precision of VLTI/GRAVITY, allow us to directly monitor the orbital movement of exoplanets with sufficient accuracy to detect the perturbing presence of exomoons. To understand and quantify the exomoon detection capabilities of different present and future instruments we have conducted a suite of blind injection and retrieval studies, simulating astrometric time series data resulting from different star-planet-moon configurations and attempting to identify such parameter spaces where detection is especially favourable. Here, we present these results for the first time, giving detailed sensitivity estimates for different instruments and putting their characteristics into context in the broader search for exomoons as well as their relevance for the future interpretation of prospective biosignature detections. The first bona fide exomoon detections are imminent. Assessing their capabilities today will strengthen the case for leveraging NIR and optical interferometry to astrometrically detect exomoons in the future.

Speaker: Thomas Winterhalder (ESO)

28 Extreme Exomoons: Unlocking the secrets of ringed and volcanic satellites

Since the advent of space telescopes such as Kepler and TESS, the discovery of exomoons has been anticipated to follow the plethora of exoplanet detections. Despite more than a decade of observations, exomoons remain elusive, with only a few candidates, such as those around Kepler-1625b and Kepler-1708b, proposed. Their physical and orbital properties challenge current theories of satellite formation and dynamics, leaving their existence under debate. This work explores the state of exomoon and exoring science, intertwining their orbital dynamics and observational characteristics to unravel the key processes shaping their evolution. We investigate phenomena such as tidal detachment leading to the formation of "ploonets" (moons transitioning into independent planets), the existence of "cronomoons" — moons with rings that could be mistaken for giant satellites — and the potential for exo-Io analogs in highly dynamic environments. A notable case is WASP-49b, which orbits its host star every 2.8 days, offering a unique testbed to study orbital stability, tidal interactions, and atmospheric signatures linked to volcanic activity. Furthermore, the search for circumplanetary rings and their potential association with massive moons provides critical insights into the mechanisms shaping these exotic systems. By combining theoretical models and observational strategies, this study aims to bridge the gaps in our understanding of exomoons and their role in the broader context of planetary system evolution.

Speaker: Mario Sucerquia (Université Grenoble Alpes)

10:30 coffee-break

Exomoons, exorings, and trojan systems

Most solar system planets have moons and rings and so we also expect them to exist around exoplanets. Co-orbital bodies (trojan) are also abundant around Jupiter and Neptune. With the current observational technology, we are at the limit of detecting these bodies and structures. Dynamical studies can tell us which planetary systems are the most favorable to look for them.

29 On the Detectability of Exomoons by Roman Galactic Bulge Time Domain Survey

Roman Space Telescope (formerly the Wide-Field Infrared Survey Telescope or WFIRST) is a NASA infrared space telescope scheduled to launch by May 2027. Wilson et al. (2023) predicted that Roman will find between 60000 and 200000 transiting planets. Through the simulated photometric uncertainties, the detectability of exomoons with various configurations hosted by these transiting planets will be investigated and presented.

Speaker: Ing-Guey Jiang (National Tsing Hua University)

30 The search for (Giant) Exorings and a Short Period Circumsecondary Disk Candidate in Orion

In our Solar system all the giant planets have rings, but their origin and evolution are still uncertain. For exorings even less is known. I will discuss the importance of a large-scale systematic search for exorings and the steps I am taking towards achieving this. Once exoring candidates have been found then they need to be characterised. Therefore, I will also discuss the enigmatic ‘Dusty Object’ in Orion. Its eclipses were first observed by NGTS in 2017 with a 0.69-day period. The eclipses are extremely asymmetric, variable, and show substructure, while the out-of-eclipse light-curve shows strong modulations. These features cannot be explained by a simple transiting planet or brown dwarf. I will discuss some of the hypotheses for this object, specifically focusing on the potential of it being a circumsecondary disk with possible exorings.

Speaker: Niamh Mallaghan (Queen's University Belfast)

Poster Session

31 Heating of planetesimals from 26Al and 60Fe

The decay of short-lived radioisotopes (SLRs) is an important source of heating for early protoplanetary systems, and can affect planetesimal and subsequent planet formation through early thermal evolution, accelerated core-mantle differentiation and volatile outgassing. However, the mechanisms by which a stellar system becomes enriched with these SLRs to levels far above the galactic background level are poorly understood. In this talk, we will discuss the methodology and results of our recent N-body simulations of stellar clusters containing massive stars, supernovae and interloping AGB stars, which were performed to determine the efficacy of these enrichment mechanisms. We will also discuss concurrent simulations modelling the effect of SLR heating on the H2O content of planetesimals, which were performed to better understand the effect of SLRs on nascent planetary systems.

Speaker: Joseph Eatson (University of Sheffield)

32 How to go from theory to observations with AI

Population synthesis is very demanding in terms of computing power. These planetary systems can however provide access to correlations, as predicted in a given numerical framework, between the properties of planets in the same system. Using AI, we can leverage such correlations that, in return, can be used to guide and prioritize observational campaigns aiming at discovering certain types of planets, such as Earth-like planets.

Speaker: Sara Marques (University of Bern)

33 Detection and Characterisation of S-type exoplanets in binaries

In recent years, transiting circumstellar (or S-type) exoplanets in binary star systems have experienced a significant expansion, notably thanks to the successful TESS space mission. Binarity is expected to impact the formation and evolution of planets, particularly when the binary separation is smaller than a few hundred astronomical units, due to the truncation of the protoplanetary disk surrounding the individual stars. We aim to confirm and further study S-type exoplanets that are part of binary systems with separations less than 200-300 AU. To this end, we have initiated a follow-up observational program targeting TESS-identified S-type exoplanet candidates. We are utilizing the recently developed near-infrared spectrograph NIRPS installed on the ESO 3.6m telescope at La Silla, Chile. NIRPS is equipped with an adaptive optics system capable of resolving binary star components down to 0.4 arcseconds.We present here the initial findings of our program,which aims to characterize planets orbiting low-mass stars (K5-M9) within these binary systems, determine which star within the binary systems is hosting a transiting exoplanet, and to measure its mass and bulk density accurately.

Speaker: Lina Messamah (University of Geneva)

34 Precise Mass Refinement of Three Sub-Neptune Systems from Radial Velocity Observations

The characterization of exoplanetary masses is essential for understanding their composition and potential for atmospheric studies. The Tracking Hydrates In Refined Small Transiting Exo-Earths (THIRSTEE) programme aims to study the composition of sub-Neptunes planets. THIRSTEE is seacrhing the answers about the composition and formation of these planets around M dwarfs or Sun-like stars, their relative occurrence, and how it dependes on other system properties. We present a detailed radial velocity analysis of three planetary systems: K2-314, K2-180, and TOI-836, all hosting sub-Neptune-sized planets ($R \sim 4 \, R_\oplus$). Using new high-precision spectroscopic data from ESPRESSO, HARPS, and HARPS-N, we refine planetary masses with a precision better than 15%. These refined mass measurements provide key insights into the internal structure and bulk composition of these planets. Additionally, we evaluate their suitability for atmospheric characterization with JWST. This study will not only improve the accuracy of mass determinations, but will also increase our knowledge of the formation and composition of sub-Neptunes, which characterise the population of candidate waterworlds.

Speaker: Samuel Geraldía González (Instituto de Astrofísica de Canarias)

35 Synthetic planetary detection rates using simulated radial velocity observations

The search for exoplanets, planets orbiting stars outside our Solar System, has become a major focus in modern astronomy. One of the most effective techniques for detecting exoplanets is the radial velocity (RV) method, which tracks tiny shifts in a star’s RV caused by the gravitational pull of orbiting planets. The goal of this project is to compute planetary detection rates, by developing a Python code that injects RV signals of synthetic planets created using the Generation III Bern model, into pre-simulated stellar RV signals. The code attempts to recover these planetary signals to compute the detection rates based on various parameters such as planetary mass, orbital period, distance from Earth, orbital phase, and inclination. These detection rates are subsequently compared to those derived in Emsenhuber et al. in prep. revealing differences in sensitivity, particularly for smaller planets and shorter orbital periods, and highlighting the advantages of the simulation-based approach in capturing nuanced detection probabilities.

Speaker: Romain Eltschinger (NCCR PlanetS)

36 Non-ideal MHD simulations of hot Jupiter atmospheres

Hot Jupiters are gas giant exoplanets that orbit their parent stars at very close distances, experiencing intense stellar irradiation. These extreme conditions lead to inflated radii, with most HJs exhibiting sizes larger than predicted by standard planetary cooling models. One possible mechanism contributing to this inflation is Ohmic heating, driven by the dissipation of currents generated through the interaction between atmospheric winds and magnetic fields. In this study, we perform 1D plane-parallel magnetohydrodynamic (MHD) simulations of HJ atmospheric columns, considering the wind and thermodynamic profiles at the substellar point coming from global circulation models of different exo-planets. We quantitatively investigate the expected effects of magnetic field winding, Ohmic dissipation, Hall drift and ambipolar diffusion. We explore several scenarios, considering profiles coming from models for different planets, with and without atmospheric magnetic drag, various background magnetic field strengths, and different domain sizes for the simulations. The main effect is the generation of strong (∼ 101 − 102 G) azimuthal magnetic field in the shear region, driven by meridional currents that generate an estimated ohmic dissipation with local efficiencies from 10−6 to 10−1, depending mainly on the atmospheric temperature, which control the conductivity. Additionally, the Hall term introduces a meridional component which can compete with the background field in the uppermost layers. In the same region, the ambipolar diffusion can become non-negligible and tends to limit the currents perpendicular to the magnetic field. The study highlights the complexity of the MHD and the need to include its effects in atmospheric modelling to determine the wind profiles and the magnetic induction.

Speaker: Clàudia Soriano (Institute of Space Sciences (ICE-CSIC))

37 Planetary Dynamos in Evolving Cold Gas Giants

Magnetic fields remain one of the least understood aspects of exoplanetary systems. A deeper understanding of planetary dynamos and the evolution of surface magnetic properties throughout a planet's lifetime is a key scientific purpose, with implications for planetary evolution, habitability, and atmospheric dynamics. This study models the evolution of magnetic fields generated by dynamo action in cold giant gaseous planets. We solve the resistive magnetohydrodynamic (MHD) equations under anelastic approximation with a 3D pseudo-spectral spherical shell MHD code. We employ 1D thermodynamical hydrostatic profiles taken from gas giant evolutionary models as the background states of our MHD models. Numerical integration leads to saturated dynamo solutions. Such calculations are performed with radial profiles corresponding to different planetary ages so that we can interpret them as different snapshots of the magnetoconvection evolution during the long-term planetary evolution. We characterize magnetic fields across different evolutionary stages of a cold gaseous planet in terms of topology and strength. We find the occurrence of a transition from multipolar to dipolar-dominated dynamo regime throughout the life of a Jovian planet. During the planetary evolution and the cooling down phase, we observe a decrease in the average magnetic field strength near the dynamo surface as ∼t−0.2−t−0.3, a trend compatible with previously proposed scaling laws. We also find that some dimensionless parameters evolve differently for the multipolar to dipolar branch, possibly reflecting a force balance change. This approach can be extended to study hot gaseous planets, offering a versatile tool for interpreting the magnetic properties of giant planets.

Speaker: Albert Elias-López (Institute of Space Sciences (ICE-CSIC))

38 Stellar Flybys are Unlikely under New Constraints from Sednoid Observation

Sednoids are extremely distant Trans-Neptunian Objects (TNOs) with large semi-major axes and large perihelion distances. To date, we have only discovered three Sedniods: (90377) Sedna, 2012 VP113, and (541132) Leleakuhonua. Sednoids are thought to have formed through a combination of early planetary scatterings, which increased their semimajor axes, and additional perturbations beyond the four giant planets, which elevated their perihelion distances. Understanding the formation mechanism of sednoids is of great significance to our understanding of the early dynamical evolution of our solar system. One hypothesis posits that close stellar flybys could have perturbed objects from the primordial scattering disk, generating the sednoid population. In this study, we run 768 N-body simulations with different stellar encounter configurations to explore whether such a close stellar flyby can satisfy new constraints identified from sednoid (and detached extreme TNO) observation, including the low-inclination ($i < 30^\circ$) profile and the primordial orbital alignment. Our results suggest that flybys with field stars are unable to generate a sufficient population, whereas flybys within the birth cluster fail to produce the primordial orbital alignment. To meet the inclination constrain of detached extreme TNOs, flybys have to be either coplanar ($i_\star \sim 0^\circ$) or symmetric about the ecliptic plane ($\omega_\star \sim 0^\circ, i_\star\sim 90^\circ$). After taking into account their occurrence rate at the early stage of the Solar System, we conclude that stellar flybys that satisfy all constraints are unlikely to happen ($<$$5\%$). Future discoveries of additional sednoids with precise orbital determinations are crucial to confirm the low-inclination tendency and the primordial alignment, and to further constrain models of the Solar System's early dynamical evolution.

Speaker: Qingru Hu (Department of Astronomy, Tsinghua University, Beijing)

39 Searching Transiting Exoplanets through Machine Learning Techniques

Due to the availability of high-performance computers and the data release from big-scale sky survey projects, the machine learning has been employed in many fields in astronomy. We have developed a numerical procedure of machine learning to search for transiting exoplanets from several survey data. Our procedure employs the convolutional neural network of deep learning techniques. In addition, another commonly-used machine learning algorithm, random forest, is also used. The details of the procedures and the results will be presented.

Speaker: Li-Chin Yeh (Institute of Computational and Modeling Science, National Tsing Hua University)

40 Exoplanet search with astrometric technique: applications to nearby exoplanet systems

The search for and characterisation of extra-solar planets is at the forefront of scientific research. My research project aims to investigate astrometric possibilities for the identification of exoplanets, to get ready to fully exploit the forthcoming huge Gaia data release, foreseen to deliver thousands of new exoplanet candidates. In the anticipation of this dataset, astrometric observations collected with Hubble Space Telescope and James Webb Space Telescope will also be exploited. Ground-based photometric and spectroscopic follow-up is needed for confirmation of Gaia exoplanet candidates, and we plan to prepare such observations. Results will provide unprecedented constraints on the distribution, orbital architectures and masses of long period giant extra-solar planets orbiting bright late-type targets in the neighbourhood of the Sun.

Speaker: Adriana Barbieri (University of Padova)

41 Architecture and masses of a (near-)resonant Kepler system through photo-dynamical modeling

The study of compact multi-planet systems provides us with unique insight into planet formation and evolution processes, particularly resonant systems that retain the architectures of early formation stages prior to destabilizing events. Within this framework, we will present a novel analysis of a two-planet system consisting of a confirmed planet and candidate companion in a possible mean-motion resonance. The study will focus on refining the architecture of the system using a photo-dynamical analysis of Kepler photometric data. The aim of this analysis is to confirm the candidate planet as well as to determine the resonant state of the system, and the planetary masses, in order to further improve our understanding of multi-planet systems.

Speaker: Marylyn Rosenqvist (Observatory of Geneva)

42 The NASA Landolt mission

The NASA Landolt mission is an astrophysics PIONEERS program small satellite that will provide significant improvement in the accuracy of photometric measurements of absolute stellar fluxes. This will be accomplished with a NIST-calibrated suite of single-mode fiber-fed laser beacons. The satellite will be placed in a near-geosynchronous orbit with a one-year primary mission with launch no earlier than October 2028. After commissioning, Landolt will point to scheduled ground-based observatories including designated ground stations and a guest observer program for calibration observations. Landolt has a level 1 mission requirement to improve the photometric accuracy to <0.5% at visible and near-infrared wavelengths for >60 target stars. Such measurements can only be achieved by a space-based orbiting artificial "star", where the emitted physical photon flux is accurately known. Accuracy of absolute flux zero points is now the leading error budget term in the characterization of stars, be they standard stars or exoplanet hosts. Landolt will enable the refinement of dark energy parameters, improve our ability to assess the properties of terrestrial worlds, and advance fundamental constraints on stellar astrophysics and evolution.

Speaker: Peter Plavchan (George Mason University)

43 PLATOSpec, new instrument for characterizing exoplanetary systems

PLATOSpec is a new echelle spectrograph with resolving power of 70,000, installed at former ESO 1.52-m telescope at La Silla. We would like to present new results from the science verification which include observing of Rossiter-Mclaughlin effect of selected systems and also stellar activity characterisation.

Speaker: Petr Kabáth (Astronomical Institute of the Czech Academy of Sciences)

44 Photometric follow-up of Young Candidate Planets

Young planets form great objects to study the early stages of planetary evolution. Due to the high activity of their host stars however, they are difficult to detect observationally. Using observations from the TESS satellite, we have compiled a list of candidate planets transiting young stars. We perform vetting through several steps such as checking background flux from nearby stars for similar signals, comparing odd and even transits to exclude eclipsing binaries, radial velocity measurements to constrain the size, and eventually photometric follow-up observations with ground-based facilities such as the 1.2 m Euler telescope (La Silla, Chile) and the 12 20 cm telescopes from NGTS (Paranal, Chile). I report on the most recent progress for our latest young, candidate planets.

Speaker: Rosa Hoogenboom (University of Geneva)

45 RHADaMAnTe: A code to estimate the SED of a wall of a gap opened by a planet in a protoplanetary disk

When a star is born, a protoplanetary disk made of gas and dust surrounds the star. The disk can show gaps opened by different astrophysical mechanisms. The gap has a wall emitting radiation which contributes to the spectral energy distribution (SED) of the whole system (star, disk and planet) in the IR band. As these new-born stars are far away from us, it is difficult to know whether the gap is opened by a forming planet. I have developed RHADaMAnTe, a computational astro code based on the geometry of the wall gap coming from hydrodynamical 3D simulations of protoplanetary disks. With this code it is possible to make models of disks to estimate synthetic SEDs of the wall gap and prove whether the gap was opened by a forming planet. I have implemented this code to the stellar system LkCa 15. I found that a planet of 10 Jupiter masses is capable of opening a gap with a curved wall with height of 12.9AU. However, the synthetic SED does not fit to Spitzer IRS SED (χ^2 ∼ 4.5) from 5µm to 35µm. This implies that there is an optically thick region inside the gap.

Speaker: Francisco Rendón (Universidad del Papaloapan)

46 Photometric study of misaligned hot Jupiter KELT-7b

Interiors of hot stars are able to conserve their angular momentum for longer time, keeping rotational velocities high for whole lifetime. If there is a planet orbiting such star, its orbit may change significantly over time. The planet may become highly eccentric, misaligned with respect to the rotational axis of the star or even undergo tidally-induced precession. Up to date, only 4 exoplanets are confirmed to be nodally precessing, but their number may grow with more long-term observations. We present the analysis of archival photometric observations of a hot Jupiter KELT-7b. Using its lightcurve, we provide updated values for the planet parameters and possible changes in the orbital configuration of the stellar system.

Speaker: Dmytro Orikhovskyi (Astronomical Institute of the Slovak Scademy of Sciences)

47 The TROY Project: Exploring Data for Orbital Indicators and Dynamics of Exotrojans

New computational capabilities allow now to squeeze existing data to explore other parameter spaces of the exoplanet population. Despite the extensive amount of Kepler data available, systematic searches for co-orbital exoplanets (exotrojans) remain unexplored. In this work, as part of the TROY project, we present a new detection method based on the dynamical properties of these systems. We have developed a dedicated algorithm that enhances the identification of co-orbital configurations by orbital dynamics rather than traditional transit detection techniques. This approach not only offers a new paradigm for the detection of exotrojans but also maximizes the scientific potential of large datasets such as Kepler’s, with future applications for missions like PLATO. We will present the first results obtained with this method, highlighting its potential to uncover previously undetected co-orbital exoplanets.

Speaker: Carmen Haukes San Lázaro (Centro de Astrobiología (CAB) CSIC-INTA)

48 Dynamical constraints on the V1298 Tau system

The V1298 Tau system is a young, four-planet system orbiting a ~20 Myr-old star, making it an ideal laboratory for studying the formation and early evolution of planetary systems. However, current estimates of the system’s orbital architecture remain poorly constrained. In particular, planetary eccentricities are largely unconstrained, and mass measurements have large uncertainties. Assuming the current orbital configuration is approximately dynamically stable, we employed a Monte Carlo approach to explore a broad parameter space of planetary masses, eccentricities, and inclinations. Our goal was to identify the most probable values consistent with long-term stability. From this analysis, we find that the outermost planet’s mass is likely near the lower bound of its currently estimated range. Moreover, despite the system likely having passed through a resonance chain during its evolution, the present-day eccentricities of all four planets are expected to be small.

Speaker: Sérgio Gomes (Anton Pannekoek Institute)

49 How Different Initial Conditions Can Affect the Configuration of Planetary Systems

My PhD research investigates the study of young planets from both observational and theoretical perspectives. These planets are undergoing various dynamic evolutionary processes, such as orbital migration, thermal contraction, and atmospheric loss, which provide valuable insights into the formation and early evolution of planetary systems. From the observational aspect, my research focuses on the detection and characterization of young exoplanets. While on the theoretical side, I am conducting simulations based on current models of planetary system formation and evolution to perform a statistical analysis of how different initial conditions influence the final configuration of planetary systems. Specifically, my research considers a model that incorporates pebble and planetesimal accretion, orbital migration, and photoevaporation within a gaseous and dusty disk. By examining factors such as the initial position of the planets, the dust surface density of the disk, and the speed of planetary migration, my study aims to identify how these key parameters affect the final architecture of planetary systems. I will present the first results from my analysis with some possible interpretations.

Speaker: Beatrice Caccherano (Queen Mary University of London)

50 The Role of the Environment in Hot Jupiter Formation and Survival

Variation in hot Jupiter occurrence rates across different stellar environments provides valuable insights into the formation and survival of these extreme planets. In this poster, I will present new results on the impact of the dynamical environment on hot Jupiter demographics and share preliminary findings from ongoing numerical studies exploring their formation in dense stellar systems.

Speaker: Mika Kontiainen (University of Cambridge)

51 Freeze out of planet inclinations in longterm exoplanet dynamics

Recent studies on the Solar System have shown that the ergodic assumption is not verified for the secular chaos, with quantities being almost conserved over planetary systems' lifetime. In particular, the total inclination angular momentum deficit (AMD), which describes the average mutual inclination of the orbits is almost conserved. This is an unexpected result since the variables are strongly influencing each-other and exchanges occur for very inclined systems (e.g. Kozai-Lidov oscillations). This conservation has an implication for understanding how planetary system evolve over long timescales but as well to constrain the occurrence rate of multi-planetary systems as the detections are strongly impacted by the mutual inclination distribution. The goal of my study is to determine when the quasi conservation is valid for typical exoplanet systems configurations.

Speaker: Sacha Kuhn (Observatoire de la Cote d'Azur)

52 Your Opportunities with ESA's CHEOPS

The European Space Agency’s (ESA’s) CHaracterising ExOPlanet Satellite (CHEOPS) is the first space mission dedicated to the search for exoplanetary transits through high-precision photometry of bright stars already known to host planets. This mission enables precise radius measurements for small exoplanets (super-Earths and sub-Neptunes), mass determinations for systems with transit timing variations, and atmospheric characterisation of highly irradiated companions. Recent science highlights include the discoveries of the first-ever hints of a glory effect on an exoplanet, not one but two six-planet systems with resonant orbits, one of the most reflective atmospheres to-date, a rugby-ball-shaped hot Jupiter, phase curves of lava worlds, and even rings around trans-Neptunian objects. Having successfully completed its 3.5-year Nominal Mission, CHEOPS is now in the middle of its first 3.25-year Extended Mission, offering the scientific community even more opportunities to get involved and apply for observing time. Come discuss your ideas and submit your proposals!

Speaker: Maximilian Günther (European Space Agency (ESA))

53 TESS Timings of 31 Hot Jupiters with Ephemeris Uncertainties

Aprecise transit ephemeris serves as the premise for follow-up exoplanet observations. We compare TESS Object of Interest (TOI) transit timings of 262 hot Jupiters with the archival ephemeris and find 31 of them having TOI timing offsets, among which WASP-161b shows the most significant offset of −203.7 ±4.1 minutes. The median value of these offsets is 17.8 minutes, equivalent to 3.6σ. We generate TESS timings in each sector for these 31 hot Jupiters, using a self-generated pipeline. The pipeline performs photometric measurements to TESS images and produces transit timings by fitting the light curves. We refine and update the previous ephemeris, based on these TESS timings (uncertainty ∼1 minute) and a long timing baseline (∼10 yr). Our refined ephemeris gives the transit timing at a median precision of 0.82 minutes until 2025 and 1.21 minutes until 2030. We regard the timing offsets to mainly originate from the underestimated ephemeris uncertainty. All the targets with timing offset larger than 10σ present earlier timings than the prediction, which cannot be due to underestimated ephemeris uncertainty, apsidal precision, or Rømer effect as those effects should be unsigned. For some particular targets, timing offsetsare likely due to tidal dissipation. Our sample leads to the detection of period-decaying candidates of WASP-161b and XO-3b reported previously.

Speaker: Susu Shan (School of Astronomy and Space Science, University of Chinese Academy of Sciences)

54 Exoplanets: Transits and Habitability

The search for life outside the Earth is one of the most ancient ambitions in humanity. Scientific and technological advances conduct the possibility to expect habitable environments even outside the Solar System, on exoplanets. The Habitable Zone (HZ) is a function of stellar parameters and represents the area surrounding a star where the surface temperature at a planet with an atmosphere is favourable to the existence of liquid water (H2O). This classic, planetary or radiative HZ contemplates inner and outer borders with temperatures of 100 and 0 °C, respectively. The definition of habitability in the Universe is biased towards terrestrial life, for which is paramount the presence of H2O as a solvent in chemical reactions between organic molecules, formed predominantly by carbon. In spite of that, the real limits for cosmic life are unknown; factors including geological phenomena, presence of an atmosphere and magnetic field on the planet and characteristics of the central star must influence it, besides the orbital dynamics of the planetary system. Particularly, the observation of transits is a significant method for exoplanet analysis, consisting in the passage of the planet in front of the stellar disk, diminishing the total flux observed from the star. These events estimate parameters such as the ratio of radius of the planet and its host star as well as the transit mid-time. We observed some transits in continuous photometry with SPARC4 (Simultaneous Polarimeter and Rapid Camera in 4 bands) in g, r, i and z bands of SDSS (Sloan Digital Sky Survey) at the 1.6m telescope in Pico dos Dias Observatory, Brazil. The priority objects were rocky planets in systems of red dwarf stars, of spectral types K and M, in order to investigate their potential habitability, along with gas giants to complete the granted nights. Therefore, differential photometry in Python scripts is applied to analyze the transits and the depth variation related with distinct wavelengths due to chemical species in the planetary atmosphere.

References [1] Deeg, H.J. and Alonso, R. 2018, Springer, 1, 633-657; [2] Deming, D. and Knutson, H.A. 2020, Nat. Astron., 4(5), 435-466; [3] Meadows, V. and Barnes, R. 2018, Springer, 1, 2771-2794; [4] NASA, Exoplanet Archive (https://exoplanetarchive.ipac.caltech.edu); [5] Wandel, A. 2023, Nat. Commun.,14(1); [6] Micela, G. 2018, Springer, 1, 1723-1736; [7] Mancini, L. et al. 2014, MNRAS, 443(3).

Acknowledgements This Master’s research is being developed with funding from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – Brasil (CAPES) - Financing Code 001 (PROEX; process 88887.904320/2023-00).

Speaker: Vitória Bellecerie da Fonseca (Universidade de São Paulo)

55 General AMD-stability criterion for exoplanet systems

The increasing discovery of extrasolar systems has made it necessary to study their stability. In this work, we present a generalization of the AMD-stability criterion defined by Laskar and Petit (2017), which defines a critical AMD-value below which close encounters are prevented and the system can be considered stable. This secular approach does not take into account mean-motion resonance overlap which can be considerable for compact multi-planet systems. We present a new AMD-framework that extends the resonance overlap criterion previously introduced by different authors. This more general approach highlights the importance of eccentricity diffusion and is also valid for 3D planetary systems. We evaluate the performance of the proposed framework on several compact two- and three-planet first-order resonant systems and discuss how the criterion could be useful for filtering observational data, thereby improving the robustness of stability predictions for newly discovered systems.
This is a joint work with A. C. Petit and A.-S. Libert.

Speaker: Justine Bodart (Université de Namur)

56 Retrograde resonant configurations in planetary systems with arbitrary masses

Using the software REBOUND [1] we explore the possible stable configurations for the 2/1, 1/2 and 1/1 retrograde mean motion resonances in planetary systems with arbitrary masses through a Monte Carlo method. The simulations were divided in two different cases: 1) varying mass of one planet; 2) varying masses for both planets. The upper limit for the masses was set to 0.012 Msun as this is near the transition between a planet and a brown dwarf [2]. The ratio of the semi-major axes and the orbital eccentricities of the planets were also varied in both simulations. We conclude that fixed point resonant families (identified by libration of all resonant angles [3]) exist for a wide range of values of the masses. Configurations with libration of a single resonant angle were also identified. Our results may be applied to identify resonant configurations amongst real extra-solar systems.

[1] Rein, Hanno e S-F Liu. “REBOUND: an open-source multi-purpose N-body code for collisional dynamics”. Astronomy & Astrophysics 537:A128, 2012.
[2] Spiegel, D. S., Burrows, A., & Milsom, J. A.,”The deuterium-burning mass limit for brown dwarfs and giant planets” The Astrophysical Journal, 727, 5, 2011.
[3] Caritá G. A., Signor A. C., Morais M. H. M., 2022, Monthly Notices of the Royal Astronomical Society, 515, 2280.

Acknowledgements: The authors acknowledge support from grants 2021/11982-5, 2022/08716-4, 2023/02528-4 & 2024/10557-7 of São Paulo Research Foundation (FAPESP).

Speaker: Helena Morais (São Paulo State University (UNESP))

57 Mapping secular migration trajectories of the ups-Andromedae system

This study explores the potential secular migration trajectories of the ups-Andromeda system over time, leading to its present-day configuration. Focusing on a model of the three-body problem, the research examines the planets c and d, which are massive and reside in orbits within the system's ice line with moderate eccentricities. By applying small dissipative disturbances, the system's total energy and orbital angular momentum are modified, thus replicating the migration process (Rodríguez, Michtchenko & Miloni, 2011). We investigated forced changes in these physical parameters using a function called Angular Momentum Leakage (Michtchenko & Rodríguez, 2011), by the matter accretion during migration. This allows us to forecast the potential secular migration paths of the system, independent of the initiating migration mechanism, relying solely on variations in total energy and angular momentum.

Speaker: Eduardo Verrone (University of São Paulo)

58 Planet dynamics during common envelope evolution of binary star

Binary stars are common and the number of systems with circumbinary planets is bound to increase with the advent of new missions like TESS, JWST. The indirect inference of planets around post-common envelope (CE) binaries has motivated investigations into their origin and survival in such violent environments. The potential existence of planets raises the question of whether the planets survived the CE stage of the binary or if they were formed from the back-falling material, after the CE has been expelled. We perform 3D global hydrodynamical simulations of the CE phase along with two first-generation planets orbiting the binary star using FLASH code. This allows us to scan the plausible parameter space of CE energy budget by varying its total kinetic, thermal and rotational kinetic energy. We then follow the dynamics of the pre-existing planets in this highly non-linear system and quantify their orbital/kinematic properties to see if they are dragged in or are ejected post-CE. Furthermore, we analyze different stellar mass-loss events obtained and identify whether a disk is formed around the close binary serving as a nursery for formation of second generation planets.

Speaker: Deepali Deepali (University of Hamburg)

12:30 lunch

Stability and dynamics of planetary systems

The orbital stability of planetary systems is not straightforward because of chaotic diffusion in the orbits. Mean-motion and/or secular resonances can help to stabilize the systems and hence put constraints on their orbital parameters to be determined from the observations.

59 Stability and dynamics of planetary systems

The remarkable diversity of exoplanetary systems has challenged our understanding of planet formation and evolution. While many systems exhibit orderly, compact architectures, others appear dynamically excited or even sculpted by past instabilities. Interpreting this diversity requires connecting theoretical models of system evolution with emerging observational constraints.

In the first part of this talk, I will explore how short-period multi-planet systems can evolve through dynamical instabilities, transitioning from compact, often resonant “peas-in-a-pod” configurations to more widely spaced and diverse orbital architectures. I will highlight recent efforts to assess the stability of these systems and to model their evolution following instability, with a focus on how these processes relate to observed trends in orbital spacing and planet sizes.

In the second part, I will turn to the role of orbital inclinations as tracers of dynamical histories. While eccentricities have long provided clues into the evolution of gas giants, inclinations—measured through stellar obliquities and mutual inclinations via astrometry—are now revealing new and sometimes surprising patterns. These include hot Neptunes on nearly polar orbits and eccentric warm Jupiters that remain strikingly spin-orbit aligned. I will discuss how such findings inform our understanding of disk-planet interactions and the long-term tidal evolution of exoplanetary systems.

Speaker: Cristobal Petrovich (Indiana University Bloomington)

60 Three-body resonances role in shaping planetary architecture

Recent works on three-planet mean motion resonances (MMRs) have highlighted their importance for understanding the details of the dynamics of planet formation and evolution. While the dynamics of two-planet MMRs are well understood and approximately described by a one-degree-of-freedom Hamiltonian, little is known of the exact dynamics of three-body resonances besides the cases of zeroth-order MMRs or when one of the bodies is a test particle. I propose the first general integrable model for first-order three-planet mean motion resonances. I show that one can generalize the strategy proposed in the two-planet case to obtain a one-degree-of-freedom Hamiltonian. The model is valid for any mass ratio between the planets and for every first-order resonance. I show the agreement of the analytical model with numerical simulations. As example of application, I show how capture in three-body first-order MMR can affect tidal dissipation, which give us constraints on the dynamical history of systems where a strong dissipation is thought to have took place such as Kepler-221.

Speaker: Antoine Petit (Observatoire de la Cote d'Azur)

61 The Resonant Remains of Broken Chains from Major and Minor Mergers

Observations with the TESS and Kepler have revealed that practically all close-in sub-Neptunes form in mean-motion resonant chains, most of which unravel on timescales of 100 Myr. Using a series of N-body integrations, we study how planetary collisions resulting from the destabilization of resonant chains produce the distribution of orbital periods observed among mature systems, focusing on the resonant fine structures that remain post-instability. In their natal chains, planets near first-order resonances have period ratios just wide of perfect commensurability, driven there by disk migration and eccentricity damping. Sufficiently large resonant libration amplitudes (of unknown origin) are needed to trigger instability. Ensuing collisions between planets ("major mergers") erode but do not completely eliminate resonant pairs; survivors which avoid mergers show up as narrow "peaks" just wide of commensurability in the histogram of neighboring-planet period ratios. Merger products exhibit a broad range of period ratios, with each resonant peak in the histogram spawning a continuum of ratios wide of the given resonance. These continua may fill in period ratios between relatively closely separated resonances such as the 5:4, 4:3, and 3:2, but may fail to bridge the relatively wide gap between the 3:2 and the 2:1. Thus a "trough" manifests just short of the 2:1 resonance (and only the 2:1 resonance), as observed. Major mergers are not perfect, and generate collisional debris which undergoes "minor mergers" with planets, in many cases further widening resonant pairs. With all this dynamical activity, free eccentricities of resonant pairs, and by extension the phases of their transit timing variations (TTVs), are readily excited. Because non-resonant planets are merger products, they are predicted to have higher masses than resonant planets.

Speaker: Rixin Li (University of California Berkeley)

62 Dynamical Instability of Multi-planet Systems and Free-floating Planets

The ejection of planets by the instability of planetary systems is a potential source of free-floating planets. We numerically simulate multi-planet systems to study the evolution process, the properties of surviving systems, and the statistics of ejected planets. For systems with only super-Earth planets, we find that the time (in units of the orbital period of the innermost planet) for the system to lose the first planet by collision or ejection increases with the semimajor axis of the innermost planet. In contrast, the time (in the same units) for the first close encounter between two planets is identical. These two timescales also have different dependence on the orbital spacing between the planets. Most systems with only super-Earths do not have planets ejected. In systems with super-Earths and a cold Jupiter, we discover that a cold Jupiter significantly increases the probability of ejection of the super-Earths by close encounters. For the super-Earths that are ejected, most of their velocities relative to their parent stars are smaller than 6 km/s. We conservatively estimate that more than 86% of the surviving two-planet systems in the super-Earths plus cold Jupiter sample are long-term stable by using empirical criteria. Most super-Earths in the remaining two-planet systems are on highly elliptical but stable orbits and have migrated inwards compared with their initial states.

Speaker: Man Hoi Lee (The University of Hong Kong)

63 Dynamics of the AU Mic system as recently observed with CHEOPS

AU Mic is a highly active M dwarf star with an edge-on debris disk and two known transiting sub-Neptunes, with a possible third planetary companion. The two transiting planets exhibit significant transit-timing variations (TTVs). We conducted ultra-high-precision photometric observations with the CHaracterizing ExOPlanet Satellite (CHEOPS) in 2022 and 2023. We combined our new measurements with results from previous years to determine the periods and amplitudes of the TTVs. Using dynamical modeling based on TTV measurements from 2018 to 2023, we reconstructed the perceived variations. AU Mic c exhibited very strong TTVs, with transits occurring approximately 80 minutes later in 2023 than in 2021. Through a dynamical analysis of the system, we found that the observed TTVs can be explained by a third planet with an orbital period of about 12.6 days and a mass of approximately 0.203 Earth masses. We explored the system's orbital geometry and found that AU Mic c is very likely on a misaligned, retrograde orbit.

Speaker: Zoltán Garai (Astronomical Institute, Slovak Academy of Sciences)

64 Resonant state of planetary systems

I provide a standardized framework based on the second fundamental model of resonance to characterize the resonant state of planetary systems. This framework allows to easily distinguish systems that evolved through tidal dissipation from other systems.

Speaker: Jérémy Couturier (Geneva Observatory)

65 Predicting the stability of planetary systems through chaos indicators

The growing number of exoplanets detected over the past three decades has created a need for fast, reliable methods to study the long-term survival of planetary systems. Here, we investigate the challenging problem of the stability of compact three-planet systems, in which resonant and chaotic processes are intrinsically linked. Four completely different chaos indicators are tested on a data set of 10,000 three-planet configurations that are in or near mean-motion resonance. On the one hand, we consider two well-established chaos indicators, namely the mean exponential growth factor of nearby orbits (MEGNO) and a modified chaos indicator based on Lagrangian descriptors. On the other hand, two non-variational chaos indicators which do not require the tangent vector computation are considered for the first time for compact systems. We evaluate the performance of each chaos indicator in correctly predicting the stability of the planetary systems, and also highlight their differences by studying the dynamics of system configurations that are inconsistently classified by different indicators. Finally, we discuss how these chaos indicators could be combined to improve overall performance and how they could be useful for imposing constraints on the orbital parameters of observed planetary systems. This is a joint work with A.-S. Libert.

Speaker: Alexandru Căliman (University of Namur)

16:00 coffee-break

Stability and dynamics of planetary systems

The orbital stability of planetary systems is not straightforward because of chaotic diffusion in the orbits. Mean-motion and/or secular resonances can help to stabilize the systems and hence put constraints on their orbital parameters to be determined from the observations.

66 Convergence of tori of maximal dimension towards tori of lower dimension in Hamiltonian systems close to integrable. Application to extrasolar planetary systems

In nearly integrable Hamiltonian systems with n degrees of freedom, KAM theory guarantees, under suitable conditions, the existence of invariant tori of maximal dimension n , foliated by quasiperiodic orbits. In addition to these maximal tori, resonant tori of lower dimension p < n may also exist. These lower-dimensional tori play an important role in the study of extrasolar planetary systems. For example, in (Couetdic et al., 2010), we designed an algorithm based on frequency analysis (FA) to locate the center of libration of a 5:1 resonance in the HD202206 system. This involved the search for a 3-torus in a 4-degree-of-freedom system. Such an orbit is of interest because, during the formation of the planetary system, dissipative effects might have driven the system toward the center of libration of the resonance. Due to observational uncertainties, the best-fit orbit may not lie exactly at this center, yet an orbit located there could potentially provide a more physically relevant configuration for the system. While the FA algorithm proved very effective in locating lower-dimensional tori, it lacked some theoretical justification. In this work, we show how the FA algorithm enables convergence to such lower-dimensional tori starting from orbits lying on a full-dimensional torus. For a specific class of Hamiltonians, we derive an analytical estimate of the convergence rate of the algorithm. These theoretical estimates are found to be in good agreement with numerical results obtained in several examples. We also provide an improved robust algorithm for this search. This is a joint work with L. Guillot.

Speaker: Jacques Laskar (Observatoire de Paris)

67 Constraints on transit-detected system architectures from formation and dynamical studies

Many transit-detected extrasolar systems harbor complex dynamical evolution governed by two-body resonances and/or chains of resonances. I will discuss how formation and dynamical studies can be useful to constrain the orbital parameters of these systems, which generally suffer from significant observational uncertainties. More precisely, I will show how i) periodic orbits can serve as dynamical clues to validate the parametrization of detected systems, ii) TTVs keep track of the migration history of planetary systems and provide signatures of three-body resonances accessible by future monitoring of the systems, and iii) the offsets in resonant chains are shaped by planetary migration and tides raised by the star.

Speaker: Anne-Sophie Libert (University of Namur)

68 Breaking cold Jupiter resonance chains with stellar flybys

Planetary migration models predict multiple planets captured into a chain of mean-motion resonances during the disk phase. Over a dozen systems have been observed in these configurations, nearly all close-in planets, with a lack of resonant chains for planets with orbital periods larger than ∼300 days. Dynamical studies often overlook the fact that stars do not evolve in isolation. In this work, we explore the possibility that the absence of giant planets in wide-period resonant chains may be due to post-formation disruption caused by stellar flybys. For planets in the 2:1-2:1 and 3:2-3:2 resonant chains, we evaluate the long-term stability after varying parameters such as the planet masses, as well as the inclination, pericentric distance, and mass of the flyby star. The encounter occurs within the secular regime, mainly perturbing eccentricities and inclinations. Our integrations show that the 2:1-2:1 resonant chain is significantly more resilient to a stellar flyby than for the 3:2-3:2 configuration. The nature of the instability is different in both scenarios, the 2:1-2:1 becomes unstable quickly, soon after a penetrative close encounter. Instead, planets in the 3:2-3:2 chain become unstable in long timescales due to more distant flybys that only provide small perturbations for the system to chaotically dissolve. If an encounter occurs between a star hosting planets and a passing star, Jupiter-mass systems with 3 planets in a 3:2-3:2 resonant chain or more compact initial configurations are likely to be disrupted.

Speaker: Carolina Charalambous (Pontificia Universidad Católica de Chile)

69 ExoNAMD: a community tool to gauge multi-planetary systems

Multi-planetary systems reveal diverse dynamical histories. Stellar obliquity is a key diagnostic of these histories, linking past dynamical interactions to migration pathways (e.g., quiescent disc vs. violent high-eccentricity). To measure the remaining dynamical violence of planetary systems, we introduce an obliquity-based NAMD (Normalized Angular Momentum Deficit), improving on the previous relative inclination-based NAMD in capturing the systems’ architectures. Our open-source ExoNAMD Python tool calculates these metrics, enabling cross-system dynamical state comparisons. The dynamical context provided by the NAMD can be used for (1) interpreting planetary atmospheres, as migration history shapes composition and thermal structure; (2) unbiased target selection for future observations and to guide model testing; (3) enabling comprehensive dynamical descriptions alongside stability indicators (AMD, MEGNO, SPOCK) in the forthcoming era of PLATO and Ariel.

Speaker: Andrea Bocchieri (Dipartimento di Fisica - Sapienza University of Rome)

70 The impact of internal versus external perturbations on close-in exoplanet architectures

Young planetary systems are subjected to different dynamical effects that can influence their orbital structure over time. In systems with more than one planet, other planets can internally influence each other, e.g. via planet-planet scattering. In addition, external perturbing effects also need to be taken into account, as stars do not form by themselves but together with other stars in young star-forming regions. This birth environment can externally affect young multi-planet systems, e.g. via fly-by encounters. Previous work has shown that the absence/presence and location of an outer Giant planet around a close-in planet system does not change how these inner planets react to a single fly-by encounter with another star. We further explore this by comparing the effects of external fly-by perturbation on four close-in Sub-Neptune planets to those caused by a situation where only the distant Giant is perturbed by the same kind of encounter. In this talk, I will show the results of several hundred N-body simulations for each of the two perturbation cases. These indicate that the close-in planet systems have a ”preferred” end state after 500 Myr, which is reached regardless of how it was perturbed. In addition, the mass of the Giant appears to not impact the reaction of the inner planet system to the fly-bys in our tested set-ups, i.e. either a single 1 or 5 M_jup Giant placed at 2.5, 5, 10 or 20 au.

Speaker: Christina Schoettler (Keele University)

71 Numerical approach to second-order canonical perturbation theory in the planetary n-body problem

Extrasolar planetary systems commonly exhibit planets on eccentric orbits, with many systems located near or within mean-motion resonances, showcasing a wide diversity of orbital architectures. Such complex systems challenge traditional secular theories, which are limited to first-order approximations in planetary masses or rely on expansions in orbital elements—eccentricities, inclinations, and semi-major axis ratios—that are subject to convergence issues, especially in highly eccentric, inclined, or tightly-packed systems. To overcome these limitations, we develop a numerical approach to second-order perturbation theory based on the Lie transform formalism. Our method avoids the need for expansions in orbital elements, ensuring broader applicability and more robust convergence. We first outline the Hamiltonian framework for the 3-body planetary problem, and apply a canonical transformation to eliminate fast angle dependencies, deriving the secular Hamiltonian up to second order in the mass ratio. We then use the fast Fourier transform algorithm to numerically simulate, in an accurate way, the long-term evolution of planetary systems near or away from mean-motion resonances. Finally, we validate our methods against well-known planetary configurations, such as the Sun-Jupiter-Saturn system, as well as to exoplanetary systems like WASP-148 and TIC 279401253, demonstrating the applicability of our models across a wide range of planetary configurations. Joint work with Jacques Laskar and Federico Mogavero.

Speaker: Aya Alnajjarine (Paris Observatory)

72 Constraining the orbit of the retrograde planet in the ν Octantis system

More than a decade ago, several studies were published in order to investigate the nature of the periodic signal in radial velocity data for the 𝞶 Octantis binary system. The most likely explanation is the existence of a planet in a retrograde orbit with respect to the binary [1]. The ratio of the orbital periods between the potential planet and the binary is close to 5/2, so the possibility of a mean motion resonance configuration arises. Using the numerical integrator REBOUND [2], we explore the phase space through random initial conditions and assess long-term stability of the system through frequency analysis [3]. Our analysis allows us to explore all possible configurations for the planet and to identify those which can be in resonance. Through this methodology, we thus conclude that a nearly coplanar 28/-11 mean motion resonance is the most probable configuration for the planet.

[1] Ramm, D., Nelson, B., Endl, M., et al., “The conjectured S-type retrograde planet in ν Octantis: more evidence including four years of iodine-cell radial velocities”, Monthly Notices of the Royal Astronomical Society, 460, 3706, 2016.
[2] Rein, Hanno e S-F Liu. “REBOUND: an open-source multi-purpose N-body code for collisional dynamics”. Astronomy & Astrophysics 537:A128, 2012.
[3] Laskar, J., "Frequency analysis for multi-dimensional systems. Global dynamics and diffusion", Physica D Nonlinear Phenomena, 67, 257, 1993.

Acknowledgements: The authors acknowledge support from grants 2021/11982-5, 2022/08716-4, 2023/02528-4 & 2024/10557-7 of São Paulo Research Foundation (FAPESP).

Speaker: Alan Signor (IGCE, Universidade Estadual Paulista (UNESP))

Wednesday 9 July

Planets in binary systems

Half of the stars in the Milky Way are in binary systems. In recent years, many planets have been found either in circumbinary configurations or around a star in a very tight binary. The existence of these planets, at the limit of stability, is very intriguing and their understanding can place many constraints on the formation process.

73 Planets in binary systems

I will review the detection methods and properties of observed exoplanets in binary star systems and how those are helpful to tease out certain physical processes during planet formation.

Speaker: Amaury Triaud (University of Birmingham)

74 A new global formation model for planets in S-type binaries

The number of planets orbiting binary stars is increasing dramatically thanks to TESS and follow-up by direct imaging/Gaia. Understanding the origin and orbital architecture of these systems requires end-to-end planet formation models, which do not exist yet for planets orbiting only one of the two stars (S-type binaries). In this talk, I will introduce a new global planet formation model for S-type systems that we are developing at the University of Geneva. This model is an adaptation of the Bern Model of Planet Formation and Evolution (e.g. Emsenhuber et al. 2021), which includes -into a single framework- solid and gas accretion, migration and N-body interactions. In the model, we have modified the structure of the protoplanetary disc to model the truncation and heating stemming from the tidal interaction of the secondary star, as well as the gravitational interactions with the stellar companion. In this talk, I will show how incorporating both of these effects alters the planet formation picture compared to the single-star case. In particular, the formation of planets in very close binaries is extremely challenging due to the limited reservoir of material available, making these systems key laboratories to constrain planet formation models, and to understand planet formation theory in general. Additionally, I will present results from CHEOPS observations of TOI candidates in blended S-type binaries, aimed at identifying which of the two stars is the true planet host, and consequently refining planet radius estimates.

Speaker: Arianna Nigioni (University of Geneva)

75 Orbital Architectures of Planet-Hosting Binaries & Triples

In stellar multiple systems, orbits on the scale of ~10 to 100 au appear to suppress planet occurrence. However, some planetary systems do form and survive in close binaries, and the reasons why provide clues to important factors in successful planet formation. The Kepler sample remains the preeminent source of planetary demographics and, crucially, is also agnostic to stellar multiplicity. I will present a decade-long astrometric survey of the closest-separation binaries among a volume-limited subset of the Kepler sample. These multiples can only be resolved with large-aperture diffraction-limited data, and adaptive optics imaging and masking from Keck/NIRC2 provides uniquely stable astrometry over very long time baselines. I will summarize some of the key findings from this long-running program, focusing in particular on the role of alignment between stellar and planetary orbital planes. With a sample size ~3x larger than previous work at these binary separations, we are now able to compare the orbital properties of different subsets of our sample, finding intriguing trends with host mass, single- versus multi-planet systems, and binary separation and mass ratio.

Speaker: Trent Dupuy (University of Edinburgh)

76 Death and Dearth of Circumbinary Planets

It has long been argued that the occurrence rate of circumbinary planets (CBPs) should be comparable to that of planets around single stars (~10%). Yet, despite the favorable geometry of eclipsing binaries for transit detection and the modeled efficiency of planet formation in circumbinary natal disks, a set of only 14 transiting CBPs have been identified to date by Kepler and TESS, suggesting a dearth in their existence. Intriguingly, all but one of these transiting planets reside at the precipice of the instability region around their binary hosts. This dearth is more striking among short-period binaries: while two-thirds of observed eclipsing binaries have periods shorter than 7 days, the shortest-period binary known to host a CBP is Kepler-47, with a period of 7.45 days. One then naturally wonders whether these signatures are real —indicative of physical evolution pathways— or merely the byproduct of instrumental limitations and observational bias, and several studies have investigated these two threads. In this talk, we propose a novel mechanism to explain the said observed features. Namely, we report on the effect of encountering a non-linear, secular resonance in the course of these systems’ expected evolution histories. When a system is adiabatically captured into this resonance, enhanced angular momentum exchange between the binary and the planet continuously pumps the planet’s eccentricity, ultimately placing it at the peril of dynamical instabilities, ejection, or engulfment by the binary.

Speaker: Mohammad Farhat (University of California, Berkeley)

77 Concealing Circumbinary Planets with Tidal Shrinkage

Of the 14 transiting planets that have been detected orbiting eclipsing binaries ('circumbinary planets'), none have been detected with stellar binary orbital periods shorter than 7 days, despite such binaries existing in abundance. The eccentricity-period data for stellar binaries indicates that short-period (< 7 day) binaries have had their orbits tidally circularized. We examine here to what extent tidal circularization and shrinkage can conceal circumbinary planets, i.e. whether planets actually exist around short-period binaries, but are not detected because their transit probabilities drop as tides shrink the binary away from the planet. We carry out a population synthesis by initializing a population of eccentric stellar binaries hosting circumbinary planets, and then circularizing and tightening the host orbits using stellar tides. To match the circumbinary transit statistics, stellar binaries must form with eccentricities > 0.2 and periods > 6 days, with circumbinary planets emplaced on exterior stable orbits before tidal circularization; moreover, tidal dissipation must be efficient enough to circularize and shrink binaries out to ~6-8 days. The resultant binaries that shrink to sub-7-day periods no longer host transiting planets. However, this scenario cannot explain the formation of nearly circular, tight binaries, brought to their present sub-seven-day orbits from other processes like disk migration. Still, tidal shrinkage can introduce a bias against finding transiting circumbinary planets, and predicts a population of KIC 3853259 (AB)b analogs consisting of wide-separation, non-transiting planets orbiting tight binaries.

Speaker: Saahit Mogan (University of California, Berkeley)

10:30 coffee-break

Planets in binary systems

Half of the stars in the Milky Way are in binary systems. In recent years, many planets have been found either in circumbinary configurations or around a star in a very tight binary. The existence of these planets, at the limit of stability, is very intriguing and their understanding can place many constraints on the formation process.

78 Detecting Circumbinary Planets via Apsidal Precession

Of the thousands of known exoplanets, only fifteen are circumbinary, oribiting two stars instead of one. All of these systems have been detected via transit photometry, which requires a low mutual inclination for all three objects to eclipse. However, over a long time baseline a wide planetary-mass companion to a binary system will induce orbital precession, modulating the relative eclipse timing of the host stars. We are conducting a search for planetary systems by identifying systems which have detectable apsidal precession over decades between observations with WASP, KELT, TESS, and others. I will present an overview of our survey, the first candidates, and future plans to confirm and characterise these potential planets.

Speaker: Benjamin Montet (University of New South Wales)

79 Evidence for a polar circumbinary planet orbiting a pair of young brown dwarfs inferred from retrograde precession

Of the types of planets orbiting binary stars, one particularly interesting category is planets with a very large mutual inclination with the inner binary, on a "polar" orbit. While polar circumbinary planets have eluded detection so far, highly misaligned and polar circumbinary gas and debris discs have been observed. Should these discs form planets it can be assumed that the corresponding polar circumbinary planets do exist. One observational signature of such an orbit is that a polar planet would induce a retrograde apsidal precession of the inner binary. Analysis of the radial velocities of a 45 Myr old binary brown dwarf reveals just such a retrograde apsidal precession. I will present this system, the properties of the potential planet, paths towards confirming it independently, and discuss how to expand on this to detect more such polar circumbinary planets.

Speaker: Thomas Baycroft (University of Birmingham)

80 Exoplanets in hierarchical triple systems

Stellar multiplicity plays a crucial role in shaping planetary system architectures. While the influence of stellar companions has been widely explored in binary systems, planets in hierarchical triple systems remain largely underexplored. The complex gravitational interplay within these systems challenges planet formation models, influencing migration, altering orbital eccentricities, and impacting long-term dynamical stability. Fewer than 40 exoplanets have been detected in triple star systems, most of them long-period gas giants discovered serendipitously. In this talk we present an observational effort to investigate planetary companions in a selection of hierarchical triple systems known to host long-period planets. By searching for inner planets within dynamically stable regions, we aim to provide empirical constraints on planetary architectures and reveal the unique characteristics of planets that exist under the gravitational influence of companion stars. Our goal is to push the boundaries of planet formation theories and enhance our understanding of planetary evolution and survival in complex, dynamically rich environments.

Speaker: Carlos Cifuentes (Centro de Astrobiología (CAB, CASIC-INTA))

81 Stability of circumbinary planets

In this work we present the latest developments in the problem of the stability of circumbinary planets and how to identify stable and unstable orbits in such systems. In this context, we carry out more than 3x10^8 numerical simulations of planets between the size of Mercury and the lower fusion boundary (13 Jupiter masses) which revolve around the center of mass of a stellar binary over long timescales. For the first time, three dimensional and eccentric planetary orbits are considered. The results of the numerical integrations are used to derive two critical borders: an outer border beyond which all planetary orbits are stable and an inner border closer to the binary below which all planetary orbits are unstable. In between the two borders, a mixture of stable and unstable planetary orbits is observed. We provide empirical expressions in the form of multidimensional, parameterized fits for the two borders that separate the three dynamical domains. Moreover, we train a machine learning model on our data set in order to have an additional tool for predicting stable and unstable motion. Both the empirical fits and the machine learning model are tested for their predictive capabilities against randomly generated circumbinary systems. The empirical formulae are also applied to the Kepler and TESS circumbinary systems, confirming the stability of the planets in these systems. Finally, the empirical fits are compared against previously derived stability criteria.

Speaker: Nikolaos Georgakarakos (New York University Abu Dhabi)

82 On the habitability of circumstellar planets in binary stars

Numerical simulations of circum-stellar planetary orbits in binary star systems show that the eccentricity of such planets can vary due to the gravitational interaction with the secondary star. The evolution of the eccentricity depends on the architecture of the binary star-planet system. We have developed methods to localize these gravitational perturbations which display It is shown that even a distant secondary star can perturb a planet in the circum-stellar habitable zone of the primary star. Here we show the possible effects for an Earth-like planet that comes closer to the Sun-like star than Venus due to an eccentric orbit, exposing it to a higher EUV flux from the host star.

Speaker: Elke Pilat-Lohinger (TU Graz)

83 A High Stellar Multiplicity Rate in the Neptunian Desert using Gaia DR3 Astrometry

An anomalous population of planets has recently been discovered in the previously barren Neptunian Desert. To understand these unusual planets it is important to recognise system and planetary properties that the Desert shares with more populous and well-studied types of exoplanets. In this work, we aim to discover whether a high stellar multiplicity rate is another of these features, shared by the Neptunian Desert planets and Hot Jupiters. We use astrometric data from Gaia DR3 to search for wide companions with consistent parallaxes and common proper motions to samples of 1779 known exoplanet hosts and 2927 exoplanet candidate hosts from the TESS mission, both within 650 pc. We find overall stellar multiplicity rates of 16.6±0.9% and 19.8 ± 0.6% for confirmed and candidate exoplanets, respectively, which are in agreement with previous studies. Splitting this sample using planetary orbital period and radius, we find stellar multiplicity rates of 16.7 ± 5.8% and 27.5 ± 2.6% for confirmed exoplanets and candidates in the Neptunian Desert, respectively. Hot Jupiter host stars were found to have rates of 25.8 ± 2.1% and 22.9 ± 1.3%. For the sample of candidate exoplanets from TESS, we find higher stellar multiplicity rates for stars hosting both Hot Jupiters and Neptunian Desert planets, compared with a control sample of similar stars not known to host planets. For the sample of confirmed exoplanets an increased multiplicity rate is seen for Hot Jupiter hosts, but cannot be significantly determined for Neptunian Desert planet hosts, due to small sample size. If the candidates from TESS are indeed planets, the increased multiplicity rate observed could indicate that the Neptunian Desert and Hot Jupiter populations share similar formation mechanisms and environmental conditions. Alternatively, the TESS candidate high multiplicity rate could imply a prevalence of false positives related to binary and triple stars in this parameter space.

Speaker: Fintan Eeles-Nolle (University of Warwick)

12:30 lunch

Synergies between theory and observations

The DDE meeting aims to bring together communities of observers and theoreticians working on exoplanets. Through the exchange of knowledge and difficulties, we hope that it will be possible to develop common strategies to extract the maximum constraints from observational data and theoretical models. It is thus important to review the successful cases and discuss new strategies to improve the interplay between theory and observations in future studies.

Thursday 10 July

Astrometry and direct imaging

Astrometry and direct imaging techniques are the only self-consistent ones as they provide the complete orbital configuration and masses of the system. Only a few planetary systems have been found to date using these techniques, but they are among some of the most interesting ones (long period orbits and young systems). Moreover, the situation is about to change drastically. The GAIA data release #4 (expected for 2026) will provide the full astrometric orbital solution of thousands of exoplanets, which is very timely for the DDE meeting.

84 Astrometry and direct imaging

Absolute astrometry and direct imaging enable the detection of (mostly) giant planets located beyond 5–10 AU – distances typically inaccessible to transit photometry and radial velocity methods. As such, they play a crucial role in probing the population of distant giant planets and testing models of planet formation. The youngest of these planets also provide unique opportunities to study interactions between planets and disks. In this talk, I will present an overview of current knowledge, including recent findings, and highlight promising prospects for the near future.

Speaker: Anne-Marie Lagrange (CNRS/Paris Observatory/PSL)

85 Astrometric jitter due to magnetic activity for Sun-like stars

Astrometric detections of exoplanets by missions like Gaia and JASMINE rely on measuring minute changes in the positions of stars - known as astrometric jitter - arising from the gravitational pull of the planetary companions. Another source of astrometric jitter is stellar magnetic activity which can interfere with the detection and characterization of Earth-mass planets through astrometric measurements. In this context, we examine the conditions under which the magnetic activity-induced jitter becomes comparable to the planet-induced jitter. Specifically, we investigate the dependence of magnetic jitter on inclination of the stellar rotation axis, stellar metallicity, configuration of magnetic features, and stellar rotation rate. We show that, for stars with solar-like magnetic activity, the jitter due to activity becomes comparable to that produced by an Earth-mass planet at 1 AU. We also find that for certain configurations of magnetic features, activity-induced jitter reaches levels detectable by Gaia.

Speaker: Sowmya Krishnamurthy (University of Graz)

86 The search for exoplanets using Gaia-DR3’s RUWE and Hipparcos-Gaia proper motion anomaly

I wish to present a new tool called GaiaPMEX, introduced in two recent papers (Kiefer et al. 2024 a, b). It characterizes the mass and semi-major axis relative to the central star (sma) of any possible companion around any source observed with Gaia. It uses for the first time the value of RUWE published in the DR3 archives, and when available, combines it with the Gaia-Hipparcos proper motion anomaly (PMa). Most importantly, it infers for any star the astrometric noises actually present in Gaia DR3 observations. It thus obtains accurate constraints on the properties of companions, debiased from possible instrument-related scatter. One of my goals is to exploit the billions of sources in Gaia's DR3 to find massive samples of exoplanet candidates to the disposal of future follow-up projects. I first focused on the 77 millions of bright (G<16) Gaia sources. Modeling their RUWE with GaiaPMEX, I identified a sample of 9,698 planet candidate hosting sources, whose companion may have a mass <13.5 MJup in the range of 1-3-au sma. This input catalog for massive exoplanets surveys will be made public soon, and I wish to explain how it has been obtained, and how it could be used by others, ahead of the publication of the DR4.
Paper I, Kiefer et al. 2024 a: https://arxiv.org/abs/2409.16992
Paper II, Kiefer et al. 2024 b: https://arxiv.org/abs/2409.16993

Speaker: Flavien Kiefer (LIRA - Observatoire de Paris)

87 Orbital Analysis of HR8799 Using GRAVITY High Precision Astrometry

HR8799 is a young multi-planet system that uniquely hosts four super-Jupiter planets and has been well-monitored through imaging and spectroscopy observations. This is the only directly imaged system for which we observe more than two exoplanets-- presenting a unique study of planet-planet interactions through astrometric measurements of high enough precision. Through the continued monitoring of HR8799 with GRAVITY, an interferometric instrument on the Very Large Telescope, we are able to further constrain the orbital parameters of this system to smaller uncertainties than previously possible. GRAVITY is capable of astrometric precision at the 10 micro-arcsecond level-- providing unparalleled constraints on the orbital parameters for all four planets. Using the newest constraints on the orbital parameters, I present an analysis on the potential formation history of the system as well as its proposed dynamical stability as derived through N-body simulations.

Speaker: Amanda Chavez (Northwestern University)

88 M15pc : The search for giant planets around M dwarfs with Gaia

M-type stars, the most common in the universe, are a major focus for surveys because they are well-suited for detecting low-mass planets in the habitable zone. Despite their importance in the formation and evolution of low-mass planets, little is known about giant planets (GPs) in M star systems. Detecting long period GPs (with semi-major axis typically greater than 1 au) is difficult with transit methods and challenging with radial velocities (RV) due to the faintness and relatively high activity level of M stars. This significant limitation can be effectively addressed by combining RV and high-contrast imaging (HCI) with Gaia-Hipparcos absolute astrometry. In this context, I used the GaiaPMEX tool presented in Kiefer et al. (2024) to detect GPs around all M stars closer than 15 pc with Gaia Data Release 3 data. GaiaPMEX uses astrometric data from Gaia and Hipparcos data when available to build a two-dimension confidence map to constrain the mass and the semi-major axis of the companion. When combining these maps with RV and HCI detection limits, we can rule out binary companions, as well as identifying and characterizing planetary companions. I built a catalog of M dwarfs within 15 pc and using GaiaPMEX, I performed a systematic search for GPs to produce a list of hundreds of planetary candidates. I will present the results of this survey which allows the study of a new population of long period GPs and in particular, to derive the radial distribution of GPs around M dwarfs beyond ~1 au.

Speaker: Florian Destriez (Observatoire de Paris)

10:30 coffee-break

Astrometry and direct imaging

Astrometry and direct imaging techniques are the only self-consistent ones as they provide the complete orbital configuration and masses of the system. Only a few planetary systems have been found to date using these techniques, but they are among some of the most interesting ones (long period orbits and young systems). Moreover, the situation is about to change drastically. The GAIA data release #4 (expected for 2026) will provide the full astrometric orbital solution of thousands of exoplanets, which is very timely for the DDE meeting.

89 Astrometric constraints on long-period planetary companions: present and DR4 perspectives

The relation between the inner and outer regions of exoplanetary systems is still an open question, for example considering that recent studies are still presenting conflicting results on the relationship between short-period small planets and cold Jupiters. One of the key obstacles to solving this issue is that the most prolific detection techniques so far are strongly biased towards short-period planets: transits can only be observed for close-in planets with the right alignment, while RVs can in principle investigate regions further away from the host star, but require huge time investment and decadal observing campaigns to find Jupiter-like planets. While direct imaging is limited to the study of young stars, astrometry can provide detailed information on the outer regions of planetary systems out to 200pc. The previous Gaia DR3 produced only a limited sample of planetary-mass candidates, limited by the short timespan of the data used and the measurement errors. This will change significantly with Gaia DR4, thanks to double the observations and an order-of-magnitude increase in precision. We present a systematic study of the populations of outer companions around known planetary systems. We perform realistic giant planets (GPs) and brown dwarfs (BDs) signal injection and recovery experiments on simulated Gaia-astrometry time series, over a volume limited (<200 pc) sample of stars with known inner planetary systems (<1AU). In absence of the true Gaia time-series, not yet publicly available, we take advantage of the Gaia Observational Forecast Tool (GOST) to simulate realistic Gaia sampling and scanning law both for DR3 and the incoming DR4. This allows us both to estimate the completeness of the current DR3 exoplanets catalog of outer companions, as well as predict the impact that DR4 will have on this topic, and how it will help solve the current uncertainty on the relationship between inner and outer exoplanet populations.

Speaker: Matteo Pinamonti (INAF - Osservatorio Astrofisico di Torino)

90 Dynamically Constraining the PDS 70 Planet Masses

Hot- and cold-start planet formation models predict differing luminosities for the young, bright planets that direct imaging surveys are most sensitive to. However, precise mass estimates are required to distinguish between these models observationally. The presence of two directly imaged planets, PDS 70 b and c, in the PDS 70 protoplanetary disk provides us a unique opportunity for dynamical mass measurement, since the masses for these planets are currently poorly constrained. Fitting orbital parameters to new astrometry of these planets, taken with VLTI/GRAVITY in the K~band, we find 95% confidence dynamical upper mass limits of 6.9 Jupiter masses for b and 15.4 Jupiter masses for c. Adding astrometry from the newly proposed planet candidate PDS 70 d into our model, we determine 95% confidence dynamical upper mass limits of 4.9, 11.3 and 4.5 Jupiter masses for b, c, and d respectively. Using these mass limits we rule out the coldest-start formation models for b, calculating a minimum post-formation entropy of 9.57 k_B/baryon. Using the mass limits from our 3-planet fit to b, c and d we also rule out the coldest-start formation models for c, calculating a minimum post-formation entropy of 8.54 k_B/baryon. This places PDS 70 b and c on the growing list of directly-imaged planets inconsistent with cold-start formation.

Speaker: David Trevascus (Max Planck Institute for Astronomy)

91 The Impact of Mean Motion Resonances on the Astrometric Detection of Giant planets

Analogues to the giant planets in our solar system are difficult to detect in the exoplanet context with our current observational methods. However, with new missions based on astrometry, these planets will become a prime population to study. The release of the Gaia DR4 catalogue in 2026, detecting ~1,000-10,000 giant planets at large orbital separations, will provide the first demographic constraints on these planets’ origins. However, performing demographic studies requires an understanding of detection efficiencies. One area that remains poorly explored in astrometric detections is the ability to detect multiple planets. In particular, the impact of an additional planet, that alone would not be detectable, on a detectable planet. There is a prevalence of near resonant systems amongst the close-in planets we have already detected, motivating the exploration of mean motion resonances on astrometric signals. We simulate the astrometric signal from multiple giant planets through N-body integrations for systems close to and far from resonance. By fitting the astrometric signal using nested sampling, which allows a Bayes evidence comparison for single and multiple planet systems as fits the data, I will discuss how resonances generate a regular pattern, allowing for the enhanced detection of close-in giant planets and resonant pairs in the Gaia dataset. Thus, when demographic studies are performed on the GAIA dataset we must account for the ability of astrometric data to distinguish between single and multiple planet solutions close to and far from resonance.

Speaker: Emmanuel Greenfield (Imperial College London)

92 Imaging and characterising forming exoplanets in their birth environment

With the ever-growing population of detected exoplanets, the startling variety in planetary configurations remains mostly unexplained. Studying planet formation in young stellar systems is a crucial step in order to truly understand this great diversity in observed exoplanets. To this end, the search for protoplanets is crucial; however, only two of them have been robustly confirmed so far, both in the same system (PDS70). HD 135344B presents a protoplanetary disk with spiral arms and a large cavity depleted of gas and dust. These structures may be due to interactions with an embedded companion, which makes HD 135344B a prime target for the search of protoplanets. We conducted a thorough analysis of archival NACO data, along with multiple SPHERE datasets obtained more recently with the star-hopping observing mode. While direct imaging generally makes use of a coronagraph to block the starlight, the star-hopping observations were captured without one in order to bypass the limitation on the inner-working angle of the coronagraph. These non-coronagraphic non-saturated observations made it possible to reach unprecedented contrasts at small angular separations within the cavity of HD 135344B. Brand new post-processing algorithms, such as IPCA (Juillard et al. 2024) and 4S (Bonse et al. 2024), were also tested on these observations. While no robust detection has been discovered so far, we identify protoplanet candidate signals, showing up in some but not all datasets, and report their significance and photometry. Upper limits on potential planetary companions have also been systematically derived within the cavity. Our observations, spanning roughly 10 years, provide a long enough baseline to study the dynamics of the spirals, as a follow-up to the study of Xie et al. 2024 using polarimetric data, which suggested the existence of a spiral-driving protoplanet on an orbit that coincides with a dust filament observed with ALMA (Casassus et al. 2021). We also present our spectral analysis aiming at identifying any protoplanet embedded within the spirals, using SPHERE-IFS and JWST-NIRCAM data.

Speaker: Justin Latour (University of Liege)

93 Detection and characterization of planetary mass objects using a multi-technique approach

Blind direct imaging (DI) surveys carried-on with state-of-the-art high-contrast imaging instruments allow to detect just a low number of new planetary mass companions due to the paucity of such objects at the typical separations explored by such instruments. The possibility to couple DI with other techniques (e.g., astrometry and RV) allows to select targets with an high probability to host a companion. Selecting young (few hundreds of Myr) and nearby (to explore the inner parts of such systems) objects, we can then improve our detection probability. Furthermore, coupling such techniques allows to better characterize both the mass and the orbital characteristics of the detected companions and to test the atmospheric models normally used to define the masses of DI companions. In some cases, this approach has yet allowed the detection of very interesting companions like, e.g., in the case of AF Lep. Finally, also in case of non-detection, the DI data acquired are able to give valuable informations on the mass and the separation of the companion causing the astrometric signal. These informations will help in designing observations with future ELT high-contrast instruments that will allow to explore the inner parts of the planetary systems even at larger distances from the Sun.

Speaker: Dino Mesa (INAF - Osservatorio astronomico di Padova)

94 Searching for exo-satellites around directly imaged companions and brown dwarf binaries using KPIC

The Keck Planet Imager and Characterizer (KPIC) is a high contrast imaging suite that feeds a high resolution spectrograph (1.9-2.5 microns, R~35,000) at the W.M. Keck Observatory. One target accessible with KPIC is GQ Lup B, a substellar companion with a detected circumplanetary disk, or CPD. Observations of the CPD suggest the presence of a cavity, possibly formed by an exo-satellite. Using high resolution, K-band spectra from KPIC, I present the first dedicated exomoon radial velocity searches around the directly imaged substellar companion GQ Lup B. Over 10 epochs, we find a median RV error of 1 km/s, most likely limited by systematic fringing, or oscillations in the spectrum’s continuum as a function of wavelength due to transmissive optics in KPIC. With this RV precision, KPIC is sensitive to exomoons 2.8% the mass of GQ Lup B at a separation of 65 Jupiter radii, or the extent of the cavity measured in the CPD detected around GQ Lup B. Additionally, I introduce a three-year KPIC survey focused on identifying spectroscopic brown dwarf binaries within 1 AU of their host stars to search for higher mass ratio companions beginning in 2023. By measuring companion RVs of 11 targets, this survey aims to better understand the occurrence rate and separation of these binaries as a function of mass ratio and distance to the host star.

Speaker: Katelyn Horstman (California Institute of Technology (Caltech))

12:30 lunch

Star-planet interactions and exoplanets' characterization

Star-planet interactions shape the orbits of close-in planets, which allow us to derive constraints for their composition. For instance, tidal interactions predict that close-in planets must be deformed and the orbits decay. From these observations it is possible to derive constraints for the inner structure of planets (Love number) and stars (Q-factor).

95 Star-planet interactions and exoplanets' characterisation

Tidal forces between short-period planets and their host stars are extreme. These lead to the deformation of the planet and the shrinkage of the planet’s orbit.. Measuring the tidal deformation of the planet would allow us to estimate the second degree fluid Love number and gain insight into the planet's internal structure. Measuring the tidal decay timescale would allow us to estimate the stellar tidal quality factor, which is key to constraining stellar physics. The community has been making a large effort to measure these effects. In particular, we are using the CHEOPS mission and JWST. I will present the CHEOPS measurements of the tidal deformation of WASP-103b and WASP-12b. Moreover, I will also present our measurements of the tidal decay of a few targets including WASP-103b and explore our future perspectives.

Speaker: Susana Barros (Instituto de Astrofísica e Ciências do Espaço)

96 Improving interior models of UltraHot Jupiters using constraints from Photometric observations

Ultra-hot Jupiters (UHJs) orbit very close to their host stars, experiencing strong irradiation and tidal forces that markedly distinguish them of the Solar System giant planets. How the interiors of these planets change due to the extreme conditions is not yet fully understood since standard interior modelling techniques using mass and radius measurements lead to degenerate results. The planet’s response to tidal forces, its tidal deformation, provides the missing observable needed to constrain the interior structure. More precisely, phase curves and transits can be used to measure the second fluid Love number for radial deformation, h2, which depends on the radial distribution of mass within the planet. In this talk, I will present a model for extracting precise h2 measurements from phase curves, showing an example of WASP-12b where the model was applied to TESS and CHEOPS observations. I will also present prospects for improving interior structure models of UHJs using Love number measurements.

Speaker: Babatunde Akinsanmi (University of Geneva)

97 From Tides to Currents: Unraveling the Mechanism That Powers WASP-107b’s Internal Heat Flux

The sub-Jovian exoplanet WASP-107b ranks among the best-characterized low-density worlds, featuring a Jupiter-like radius and a mass that lies firmly in the sub-Saturn range. Recently obtained JWST spectra reveal significant methane depletion in the atmosphere, indicating that WASP-107b’s envelope has both a high metallicity and an elevated internal heat flux. Together with a detected non-zero orbital eccentricity, these data have been interpreted as evidence of tidal heating. However, explaining the observed luminosity with tidal dissipation requires an unusually low tidal quality factor of Q ~ 100. Moreover, we find that secular excitation by the RV-detected outer companion WASP-107c, generally cannot sustain WASP-107b’s eccentricity in steady state against tidal circularization. As an alternative explanation, we propose that Ohmic dissipation — generated by interactions between zonal flows and the planetary magnetic field in a partially ionized atmosphere — more naturally maintains the observed thermal state. Under conservative assumptions for the field strength, atmospheric circulation, and ionization chemistry, we show that Ohmic heating readily accounts for WASP-107b’s inflated radius and anomalously large internal entropy. In light of this result, tidal mechanisms need not contribute significantly to WASP-107b’s present-day energy budget, reconciling the tension between the system’s age and measured eccentricity with a tidal quality factor Q > 10,000.

Speaker: Konstantin Batygin (Caltech)

98 Ohmic inflation of Hot Jupiters

The inflated radii observed in hundreds of Hot Jupiters (HJs) represents a long-standing open issue, with Ohmic dissipation being one of the most promising mechanisms for a quantitative explanation. In this study, inspired by results from evolutionary models in the last decade, we specifically delve into the inferrance of the amount of electrical currents induced by the atmospheric winds. Using the evolutionary code MESA, we simulate the evolution of irradiated giant planets, spanning the observed range of masses and equilibrium temperatures, a plausible range of core sizes and compositions. We incorporate an internal source of Ohmic dissipation that extends to deep layers of the envelope, accounting for electrical currents proportional to the electrical conductivity, given by thermal ionization of alkali metals and pressure-ionization of hydrogen at deeper layers. We explore how, varying the intensity of currents, we can broadly reproduce the range of observed radii. As a by-product, using classical scaling laws which relate the deep-seated and surface magnetic fields to mass, structure and internal luminosity, we predict that heavy planets are much more likely to have large surface fields of hundreds of G.

Speaker: Daniele Viganò (Institut de Ciències de l'Espai (ICE, CSIC-IEEC))

99 From Misaligned Hot Jupiters to Aligned Warm Jupiters: Constraining Qp of Jupiters

One of the most surprising and intriguing findings in exoplanetary configurations is that hot Jupiters are often spin-orbit misaligned. In this talk, I will present new Rossiter–McLaughlin observations showing that, by contrast, single-star warm Jupiter systems tend to remain aligned. The sharp transition from misaligned hot Jupiters to aligned warm Jupiters suggests that high-eccentricity migration—effective only in producing very close-in planets (e.g., hot Jupiters) through tidal circularization—is responsible for these misalignments. This provides an unprecedented opportunity to constrain the tidal dissipation rates of Jupiters. I will discuss the new constraints we have placed on the effective equilibrium tidal factor and offer insights into the tidal dissipation rate during the high-eccentricity phase.

Speaker: Songhu Wang (Indiana University)

15:30 coffee-break

Star-planet interactions and exoplanets' characterization

Star-planet interactions shape the orbits of close-in planets, which allow us to derive constraints for their composition. For instance, tidal interactions predict that close-in planets must be deformed and the orbits decay. From these observations it is possible to derive constraints for the inner structure of planets (Love number) and stars (Q-factor).

100 Tidal destruction of ultra-short-period planets around Sun-like stars

Chemical evidence indicates that an appreciable fraction of Sun-like stars have engulfed rocky planets during their main-sequence lifetimes. We investigate whether the tidal evolution and destruction of ultra-short-period planets (USPs) can explain this phenomenon. We develop a simple parameterized model for the formation and engulfment of USPs in a population of MS stars. With this model, it is possible to reproduce both the observed occurrence rate of USPs and the frequency of planet-engulfing Sun-like stars for a reasonable range of USP formation rates and tidal decay lifetimes. Our results support a theory of USP formation through gradual inward migration over many Gyr and suggest that engulfment occurs ~0.1-1 Gyr after formation. This lifetime is set by tidal dissipation in the USP itself instead of the host star, due to the perturbing influence of external companions. If USP engulfment is the main source of pollution among Sun-like stars, we predict a correlation between pollution and compact multi-planet systems; some 5-10% of polluted stars should have a transiting planet of mass >5 Earth masses and period ~4-12 days. We also predict an anti-correlation between pollution and USP occurrence.

Speaker: Christopher O'Connor (CIERA, Northwestern University)

101 Tidal Dynamics and Rotational States of TRAPPIST-1 Planets: Implications for Observations

Recent JWST observations of the thermal emission from TRAPPIST-1 b and c have provided new constraints on their possible atmospheres (Greene et al. 2023; Ih et al. 2023; Zieba et al. 2023; Lincowski et al. 2023). In this context, accurately modeling their rotational states and tidal heating is essential for interpreting these observations. A widely accepted assumption is that the TRAPPIST-1 planets have reached a synchronous rotational state due to tidal evolution. However, our simulations indicate that planet-planet interactions prevent exact synchronization with their orbital motion. These interactions induce sub-stellar point drifts that lead planets to experience day-night cycles, with solar day lengths ranging from 43 to 656 years, depending on the planet. Tidal dissipation within a plane can significantly impact its thermal state, as observed in Io, the Solar System's most volcanically active body (Renaud et al. 2018; Kervazo et al. 2021). Recent constraints on the nightside brightness temperatures of TRAPPIST-1 b provide upper limits on the tidal heat flux, offering insights into the planet's rotational state and obliquity for a given internal structure (Ducrot et al., in revision). Additionally, different internal structures lead to varying dissipation rates, which can produce measurable effects on Transit Timing Variations (TTVs). These variations may serve as a key observational tool to distinguish between different internal compositions and dissipative properties of the TRAPPIST-1 planets.

Speaker: Alexandre Revol (Geneva University)

102 Advancing JADE: Evolution of hot Sub-Neptunes with Water-Enriched Atmospheres

Exoplanets in the hot Neptune desert, with their proximity to host stars and limited envelope masses, challenge our understanding of planetary evolution. Their survival despite expected significant atmospheric loss raises questions about their origins and the mechanisms shaping their evolution. To address these complexities, JADE (Joining Atmosphere and Dynamics for Exoplanets) was developed to couple secular orbital evolution with atmospheric loss over long timescales. JADE reproduced the misaligned orbit of GJ 436 b, a warm Neptune, revealing the interplay between high-eccentricity migration and delayed atmospheric escape. However, the current version of JADE assumes a pure H/He envelope, which may not fully represent small Neptunes and sub-Neptunes, as these planets likely exhibit higher envelope metallicities and molecular compositions. We now extend JADE by incorporating water into H/He-dominated envelopes, with refinements in opacity, equation of states for density profile, and mass loss rates. I will show how these advancements enable more realistic simulations of close-in planets' atmospheres, exploring how they bloat or shed their envelopes in response to the intricate dance orchestrated by their host stars and outer companions. We aim to expand JADE's applicability to a broader range of exoplanetary systems and welcome collaborations emerging from this conference.

Speaker: Emily Wong (Geneva Observatory)

103 To be or not to be a planet: multi-wavelength verification of deep desert Neptunes

Very few planets have been discovered in the Neptunian desert, a region of period-radius parameter space encompassing Neptune-sized, short-period planets. The lack of planets in this region is explained by photoevaporation and high-eccentricity migration coupled with tidal disruption. However, since the launch of TESS a handful of planets have been discovered deep inside the Neptunian desert, defying formation and evolution theories, and several more candidates remain open to question. Confirming the existence of more deep desert planets would point at unusual formation and evolution pathways for close-in Neptune-sized planets. However, one dangerous source of false-positives in this candidate population is hierarchical triple systems. Hierarchical triple systems have a compact inner binary and a more distant outer tertiary star. If the inner binary eclipses, it can mimic the transit of a Neptune-sized planet, due to dilution from the tertiary companion, and the presence of the tertiary companion is extremely difficult to identify with radial velocity measurements. Observing changes in the transit depth when observing in different wavelengths is the best technique to distinguish an eclipsing inner binary from a transiting Neptune. We present the results of simultaneous multi-wavelength photometry of 6 deep desert Neptunes with MuSCAT.

Speaker: Isobel Lockley (University of Warwick)

104 Diversities and similarities exhibited by multi-planetary systems

The rich diversity of multi-planetary systems and their architectures is greatly contrasted by the uniformity exhibited within many of these systems. Previous studies have shown that compact Kepler systems often exhibit a peas-in-a-pod architecture: Planets in the same system tend to have similar sizes and masses and be regularly spaced in orbits with low eccentricities and small mutual inclinations. In this talk, I will introduce the work in my recent paper on the orbital architectures of most of the observed multi-planetary systems, including the Solar System. Compared to previous research, I examined a larger and more diverse sample of systems, focusing on the orbital spacings between adjacent planets as well as their relationships with the planets’ sizes and masses. I also quantified the similarities of the sizes, masses, and spacings of the planets within each system, conducting both intra- and inter-system analyses. I will show some of the results from these investigations and present the main conclusions.

Speaker: Alexandra Muresan (Chalmers University of Technology)

Conference Photo

Friday 11 July

TTVs and transit-detected compact systems

The transit technique is the most successful one to detect planets. For single planets it provides a direct estimation of their radius. However, in multi-planet systems, the transit timing variations (TTVs) induced by mutual perturbations can provide additional invaluable information in their masses and densities. They can also reveal the presence of unseen non-transiting planets. It is therefore extremely important to correctly model the TTVs to extract a maximum of constraints on these planetary systems.

105 Architecture of resonant systems of sub-Neptunes: constraints from transit timing variations

Resonances are a natural outcome of the migration of exoplanets. Consequently, they appear to be a crucial step in the formation of close-in sub-Neptunes. These exoplanets, with radii ranging from 1 to 4 Earth radii and orbital periods of less than 100 days, have been shown to exist around 30 to 50% of sun-like stars, based on early results from the HARPS spectrograph and the Kepler spacecraft.

A leading model for the formation of this population is called "breaking the chains." In this model, close-in systems of sub-Neptunes form in resonant chains due to the migration of planets in protoplanetary disks. After the disk dissipates, most resonant chains become dynamically unstable. The chains that survive then evolve through tidal forces over timescales of billions of years. Although resonant configurations represent only a few percent of transiting systems, they are crucial to understanding the formation and evolution of about half of planetary systems. The intricate details of the architecture of resonant exoplanets encode their history. We can access these architectures by observing the effect of planet-planet gravitational interactions on the timing of planetary transits, known as the transit timing variation (TTV) method.

However, TTVs present challenges: for shallow transits, the use of non-adapted methods can lead to non-detection of planets or erroneous TTV measurements, which in turn biases the estimated masses. For some configurations, the mass can be affected by a degeneracy between the recovered mass and eccentricity. Additionally, non-transiting planets can also affect the observed TTVs. During this talk, I will discuss the TTV-related challenges and the state-of-the-art methods to alleviate them. I will then describe how these issues potentially impacted major statistical results of the 2010s, notably the apparent paucity of exoplanetary systems within resonances, and the apparent low density of TTV-characterized planets.

Speaker: Adrien Leleu (Université de Genève)

106 Detection of Inner Companions of Hot Jupiters through Transit Timing Variations

Transit Timing Variations are a powerful method for detecting and studying additional planets in exoplanetary systems. Hot Jupiters, massive gas giants orbiting very close to their stars, were once thought to exist in isolated orbits. However, recent discoveries of small nearby companions, have shown that these systems can be more complex. By analyzing TTVs, we can measure the masses, orbital periods, and interactions of these companions, even if they do not transit or are undetectable by traditional methods like radial velocity. Systems with TTVs are also excellent laboratories for studying planetary formation and migration, offering insight into how planets settle into resonant or near-resonant configurations. The study of TTVs in hot Jupiter systems challenges previous theories about how these planets form and evolve, revealing new complexities in planetary systems. With high-precision photometric data, TTV analysis continues to uncover hidden planets and improve our understanding of the dynamics and architecture of exoplanetary systems. In this talk, I will present the latest photometric observations of hot Jupiter systems, focusing on their dynamical interactions with close-in companions.

Speaker: Judith Korth (Lund University)

107 Stretching the limits of TTV analysis

We used PyDynamicaLC, a photodynamical model tailored for the analysis of the smallest- and lowest-TTV-amplitude- planets, to analyze Kepler’s multi-planet systems (Ofir+2025), where we were able to determine significant masses to 88 planets. We demonstrate consistency with literature results over 2 orders of magnitude in mass, and for the planets that already had literature mass estimations, we were able to reduce the relative mass error by ∼22% (median value). Of the planets with determined masses, 23 are new mass determinations with no previous significant literature values, including a planet smaller and lighter than Earth (KOI-1977.02/Kepler-345 b). I will also put the above discoveries in a wider context of the limits of shallow signal identification and the benefits of photodynamical modeling vs. classical TTV analysis, as they manifest themselves differently in signal detection, in modeling relatively high SNR systems, and in limited (but still possible) analysis of low-SNR systems.

Speaker: Aviv Ofir (Weizmann Institute of Science)

108 Fascinating Transit Timing Variations of Hot Jupiters: Evidence of Planet Migration

Transit timing variations (TTVs) of hot Jupiters can reveal signatures of multiple physical processes, including apsidal precession, the Rømer effect, and notably, planetary migration. Hot Jupiters are believed to form at significant distances from their host stars and later migrate inward, a scenario that can be directly supported by TTV measurements. Detecting TTVs requires a long observational baseline and high precision in determining transit midpoints. Leveraging the full-sky coverage and continuous monitoring capabilities of TESS, we have launched a campaign to monitor the long-term TTVs of known hot Jupiters. As part of this effort, we have reported TTV detections for WASP-161b, K2-237b, and XO-3b, augmenting our observations with additional data from approved proposals using CHEOPS and ground-based telescopes. Our analysis suggests that a period decay model best explains the TTVs of WASP-161b. However, the inferred tidal quality factor is remarkably low—comparable to that of rocky planets in the Solar System—despite WASP-161b being a gas giant. This rapid orbital decay likely indicates an exceptionally efficient transfer of orbital energy into the planet's or host star's interior, or it may be driven by alternative mechanisms, such as magnetic interactions. For K2-237b, we detected a period decay, with additional evidence suggesting the presence of a circumstellar disk. Infrared excess was observed at a significance level of 1.5σ in the WISE W1 and W2 bands, and at 2σ in the W3 and W4 bands, based on spectral energy distribution fitting. To further investigate the physical origins of the period decay, we are developing a star-planet interaction model that considers both magnetic and tidal interactions simultaneously. For magnetic interactions, the package incorporates the magnetic topology of the host star and the orbital characteristics of the planet. For the tidal interaction, the package includes empirical equations for both equilibrium and dynamic tides.

Speaker: Fan Yang (CEA, University of Paris-Saclay)

109 A decade of transit photometry for K2-19: breaking the mass-eccentricity degeneracy

K2-19 hosts a pair of Neptune-like planets inside the 3:2 resonance, with previously reported eccentricities of 0.2 raising questions about conditions at the time of formation. Moreover, in spite of the system's resonant status both resonance angles circulate at these high eccentricities, contrary to common understanding. Tripling the observing baseline reveals the full resonant evolution of the TTVs and elements, and constrains the eccentricity posterior to median values of 0.04 and 0.07 for the inner and outer planets. Planet masses are constrained to within 4% and are completely uncorrelated with the eccentricities. I will present these results as well as an intuitive new formalism for studying two-planet systems near a first-order commensurability, using it to describe the circumstances under which masses and eccentricities are decoupled in systems exhibiting transit timing variations, as well as to show that transit duration variations cannot be used to measure the true eccentricities.

Speaker: Rosemary Mardling (Monash University)

10:30 coffee-break

TTVs and transit-detected compact systems

The transit technique is the most successful one to detect planets. For single planets it provides a direct estimation of their radius. However, in multi-planet systems, the transit timing variations (TTVs) induced by mutual perturbations can provide additional invaluable information in their masses and densities. They can also reveal the presence of unseen non-transiting planets. It is therefore extremely important to correctly model the TTVs to extract a maximum of constraints on these planetary systems.

110 TESS warm-Jovian exoplanets with strong TTVs

Recent TESS discoveries have revealed increasing number of exoplanetary systems exhibiting strong transit timing variations (TTVs), many of which consist of warm, Jovian-mass planet pairs near a 2:1 mean-motion resonance (MMR). I will present several peculiar TTV systems identified within the Warm gIaNts with tEss (WINE) collaboration, which systematically characterizes TESS transiting warm giant planets. These systems are particularly valuable for exoplanet studies, as their longer orbital periods amplify TTV signals, allowing for the detection of non-transiting companions and precise constraints on their orbital architecture and physical properties. However, strong TTV signals also introduce degeneracies in planetary mass, eccentricity, and even orbital period, complicating system characterization. To resolve these ambiguities, TTV modeling, photo-dynamical analysis, and ground-based RV follow-up are essential. By combining these techniques, we can reverse-engineer the formation and dynamical evolution of compact, massive planetary systems, shedding light on their migration history and resonant interactions. I will discuss the challenges in modeling such multi-planet systems, the impact of dynamical interactions on their architectures, and how the synergy between TTVs and RVs provides a powerful tool for uncovering the formation pathways of warm Jupiters and their companions.

Speaker: Trifon Trifonov (Landessternwarte, Zentrum fur Astronomie der Universtat Heidelberg)

111 Transit Timing Variations in HIP41378: CHEOPS and TESS probe the architecture of a six-planet system

In multiple-planet systems, gravitational interactions of exoplanets could lead to transit timing variations (TTVs), whose amplitude becomes significantly enhanced when planets are near mean-motion resonances (MMRs), making them more easily detectable. In cases where both TTVs and radial velocity (RV) measurements are available, combined analysis can break degeneracies and provide robust planetary, and system characterization. In this context, HIP 41378 hosts five transiting planets with periods ranging from 15 to over 540 days, providing a unique dynamical laboratory for investigating wide multi-planet systems analogous to our own. In this study, we present an intensive space-based photometric follow-up of HIP 41378, combining 15 new CHEOPS observations with eight TESS sectors, alongside data from K2, Spitzer, HST, and 311 HARPS spectra. Using the N-body integrator within TRADES, we dynamically modeled the TTVs and RV signals of the two inner sub-Neptunes. These planets, HIP 41378 b (Pb = 15.57 days, Rb = 2.45 R⊕) and HIP 41378 c (Pc = 31.71 days, Rc = 2.57 R⊕), are nearly (~1.8%) in a 2:1 period commensurability. We report a clear detection of anti-correlated TTVs with amplitudes of 20 minutes for planet b and greater than 3 hours for planet c. We dynamically confirm the planetary nature of HIP 41378 g, a non-transiting planet with a period of about 64 days and a mass of about 8 M⊕, close to a 2:1 commensurability with planet c, suggesting a possible mean-motion resonance chain in the system. Our precise determination of the masses, eccentricities, and radii of these planets enabled us to constrain their volatile-rich compositions and reconstruct the evolutionary histories of their primordial atmospheres. Additionally, we demonstrated how the two inner planets are excellent candidates for atmospheric characterization with the NIRSpec/Prism instrument aboard JWST. Finally, we provide new insights into the three outer planets (P > 300 days), constraining the period of HIP 41378 d and suggesting a number of aliases for HIP 41378 e. Our analysis suggests that the system could be placed in a double resonant chain, highlighting its complex dynamical architecture.

Speaker: Pietro Leonardi (Università degli studi di Padova / Università di Trento / INAF OAPd)

112 Transit timing variations with NGTS

Measuring transit timing variations allows us to study multi-planet systems, in particular probing planetary masses and dynamics. NGTS, with its high photometric precision, fast cadence and flexible scheduling, is very well suited to measuring transit timing variations . Here we present the suite of NGTS projects aimed at measuring transit timing variations over a range of targets and science cases. We showcase the results we have to date, and discuss the future prospects in the context of the extended TESS mission and the upcoming PLATO mission.

Speaker: Daniel Bayliss (University of Warwick)

113 Exceptionally Large Transit Timing Variations in TOI-4504: A Tale of Resonance and Complexity

We present the discovery and analysis of exceptionally large transit timing variations (TTVs) in the TOI-4504 exoplanetary system. Using data from NASA's Transiting Exoplanet Survey Satellite (TESS) and radial velocity measurements from FEROS, we identified TOI-4504 c as a warm Jupiter with a peak-to-node TTV amplitude of approximately 2 days, the largest such signal observed to date. Dynamical modeling revealed the presence of a nontransiting gas giant, TOI-4504 d, which together with TOI-4504 c forms a stable pair likely in a 2:1 mean-motion resonance. Additionally, TOI-4504 b, a hot sub-Neptune, was identified in the system, contributing further to the complexity of this multi-planetary architecture. This system provides valuable insight into the formation and long-term stability of resonant gas giant pairs and highlights the power of combining TTV and radial velocity techniques for characterizing complex planetary architectures.

Speaker: Michaela Vítková (Astronomical Institute of the Czech Academy of Sciences)

114 Uniform search of new TESS transiting candidates in the Neptunian desert

The Neptunian desert, a scarcity of Neptune-like planets in close orbit around their host stars, is an unexpected finding of the known exoplanet population. Large space-based surveys like TESS, together with ground-based follow-up, are identifying and confirming new transiting planet candidates in and near the desert. However, the targets that end up being followed form a heterogeneous and biased sample. Hence, the current population of planets in and near the desert is incomplete and highly biased. We performed a search for transiting planet candidates in a homogeneous, magnitude-limited sample of main sequence stars well-characterised by Gaia and observed by TESS (almost 2.3 million stars). We applied the new automatic vetting and validation pipeline RAVEN to the TESS data of our stellar sample. This pipeline allows us to find transiting candidates and obtain the probability of them being true planet candidates rather than common false positives, accounting for biases. Hence, we statistically validated several new transiting planet candidates. This uniform search for planets will reveal the radius distribution of planets in and near the Neptunian desert in a statistically robust way. This uniform, well-defined sample, will be invaluable to inform formation and evolution models and to understand the demographics of planets in the desert.

Speaker: Marina Lafarga Magro (University of Warwick)

115 Demographics of Close-In TESS Neptunian Planets Orbiting FGK Stars

Understanding the demographics of close-in Neptune-sized planets is a key to exploring planet formation, particularly around the Neptunian desert. We performed a comprehensive search of TESS SPOC Full Frame Image light curves to identify transit signals. Candidate validation was conducted with our RAVEN pipeline, utilizing machine learning to identify false positives. The resulting sample enabled a robust statistical occurrence rate estimation for close-in Neptunes orbiting FGK stars, offering critical insights into their distribution and the processes shaping planetary system architectures.

Speaker: Kaiming Cui (University of Warwick)

116 Multi-methods extraction of TTVs for (near-)resonant systems in Kepler, TESS and PLATO

The detection of exoplanets rely heavily on space-based transit surveys such as Kepler, TESS and PLATO. In these surveys, detecting and characterising small planets pose challenges due to their low signal-to-noise ratio (SNR). Standard methods, such as the Box least square (BLS) algorithm, exploit the periodic nature of orbits to enhance the SNR. But these methods are fundamentally limited when gravitational perturbations between the planets disturb the periodic nature of their orbit. These perturbations lead to transit timing variations (TTVs), causing smearing of the transits and reduction of the detection significance. This can lead to an underrepresentation and inaccurate characterization of small planets embedded in resonant systems. Consequently, there is a necessity for flexible approaches that capture these signals. Prominent examples include for example QATS [Carter et al. 2013], RIVERS [Leleu et al. 2021] and an adapted approach of the Radon algorithm [Copeland et al. 1994]. After exposing the problem of detecting quasi-periodic signals, I will present adapted methods and my ongoing work to improve them. I will also present a comparison of the performance of these methods on real and synthetic data, before illustrating these results by the confirmation and characterisation of a new resonant pair of planets.

Speaker: Yannick Eyholzer (University of Geneva)

12:45 lunch

Formation and evolution of planetary systems

By better understanding how a planetary system was formed and evolved into the currently observed configuration, we can put constraints on the planetary composition and initial planetary disk. We can also determine if the climates of the planets in the habitable zone can be stable over billions of years such that life can develop.

117 Formation and evolution of planetary systems around stars of different masses and metallicities

The formation and evolution of planetary systems are linked to their host stellar environment. Here we employ a pebble accretion planet formation model to explore the correlation between planetary properties and stellar mass/metallicity. Our numerical results reproduce several main aspects of exoplanetary observations. First, we find that the occurrence rate of super-Earths ηSE follows an inverted V-shape in relation to stellar mass: it increases with stellar mass among lower-mass dwarfs, peaks at early-M dwarfs, and declines toward higher-mass GK stars. Second, super-Earths grow ubiquitously around stars with various metallicities, exhibiting a flat or weak ηSE dependence on stellar metalicity. Third, giant planets, in contrast, form more frequently around stars with higher-mass/metallicity. Lastly, we extend a subset of simulations to 1 Gyr to investigate the long-term evolution of the systems’ architecture. By converting our simulated systems into synthetic observations, we find that the eccentricities and inclinations of single-transit systems increase with stellar metallicity, while these dependencies in multi-planet systems remains relatively weak. The alignment between our results and observations provides key insights into the connection between planet populations and stellar properties.

Speaker: Beibei Liu (Zhejiang University)

118 A swarm of dusty objects in orbit around the central star of planetary nebula WeSb 1

Exoplanets and smaller bodies have been detected orbiting different kind of stars. However, we do not know of any such objects in planetary nebulae, the short-lived stage of stellar evolution between the asymptotic giant branch and white dwarf phases. The planetary activity (destruction and formation) may be accompanied by dust clouds. Hence, we searched for dust occultation events in planetary nebulae using archival photometric data. We show that the central star of PN WeSb 1 features numerous dimming events with typical durations of a few days to weeks that are up to 3 mag deep. This variability is mainly stochastic with an indication of a 400 d period. The occultations are almost grey, indicating dust grains larger than about 0.1 μm. Based on our follow-up observations, we argue that the central star is a wide binary and that these events are most probably caused by debris from disintegrated small rocky bodies that escaped from the former asymptotic giant branch star to find safe harbour around the companion star. The latter star dominates the optical spectrum enabling us to see the eclipses. This means that planetary systems are present and undergo violent evolution during the planetary nebula stage.

Speaker: Jan Budaj (Astronomical Institute, Slovak Academy of Sciences)

119 Mutually-aligned orbits revealed by a Rossiter-McLaughlin analysis of the planetary system GJ 9827

The GJ 9827 system hosts three planets in near-resonant orbits, smaller than two Earth radii. The two inner planets have an Earth-like composition, while the outer companion is a mini-Neptune with a volatile envelope. These features raise questions about the roles of in-situ formation and inward migration in shaping the system, which can be addressed by measuring the orbital architectures of the planets. GJ 9827 offers a rare opportunity to derive and compare the 3D spin-orbit angle of three small planets transiting the same star. We obtained transit observations of each planet as part of the ESPRESSO GTO and used a novel workflow, ANTARESS, to reduce the data homogenously and perform a joint Rossiter-McLaughlin "Revolutions" analysis of the three transits. We present our findings for the system's architecture, aiming to enhance our understanding of planetary system dynamics and composition. We find the three planets to be mutually aligned and orbiting within the stellar equatorial plane, favouring a scenario where the star and protoplanetary disk remained aligned, and the three planets migrated early on within the disk.

Speaker: Erik Fridén (Univeristy of Geneva)

120 Evidence that Planets in the Radius Gap Do Not Resemble Their Neighbors

Planets in compact multi-transiting systems tend to exhibit self-similarity with their neighbors, a phenomenon commonly called "peas-in-a-pod". Previous studies have identified that this self-similarity appears independently among super-Earths and sub-Neptunes orbiting the same star. In this study, we investigate whether the peas-in-a-pod phenomenon holds for planets in the radius gap between these two categories (located at ~1.8 R⊕). Employing the Kepler sample of planets in multi-transiting systems, we calculate the radius ratios between radius gap planets and their neighbors. We find that in systems in possession of a radius gap planet, there is a statistically significant deficit of planet pairs with radius ratios near unity. We find that neighbors to radius gap planets actually exhibit reverse size-ordering (that is, a larger inner planet is followed by an outer smaller planet) more often than they exhibit self-similarity. We go on to compare whether the period ratios between neighboring planets also differ, and find that radius gap planets are likelier to reside in mean motion resonance with neighbors, compared to non-gap planets (particularly in the 3:2 configuration). We explore the possibility that systems with a radius gap planet may be modified by a process other than photoevaporation or core-powered mass loss. The appearance in tandem of unusual size-ordering of gap planets in multi-planet systems, together with unusual spacing, furnishes potential supporting evidence in favor of giant impacts sculpting the radius distribution to some degree.

Speaker: Quadry Chance (University of Florida)

Stability and dynamics of planetary systems

The orbital stability of planetary systems is not straightforward because of chaotic diffusion in the orbits. Mean-motion and/or secular resonances can help to stabilize the systems and hence put constraints on their orbital parameters to be determined from the observations.

121 Stability and dynamics of the compact planetary system K2-72

We consider the dynamic evolution of the compact four-planetary system K2-72. Star K2-72 is an M-type dwarf. The system contains three Earth-like planets and one super-Earth. We searched for low-order resonances within the uncertainty of determining the periods of the planets. We considered a few scenarios for the evolution of the K2-72 system over 100 Myr using the Posidonius software, which considers tidal interactions. Furthermore, we showed that the compact planetary system K2-72 is likely to evolve beyond low-order resonances. A significant change in the large semi-major axes of the orbits of the K2-72 b and K2-72 d planets leads to the moving of the adjacent planets b–d and d–c out of the 7/5 and 8/5 resonance regions, respectively. The adjacent planets K2-72 d and K2-72 c are located far from the 2/1 resonance, which excludes the possibility of forming chains of mean motion resonances and, hence, 3-planet mean motion resonances. If the orbital eccentricities do not exceed 0.03, the evolution of the compact planetary system K2-72 over 100 Myr remains stable even in the presence of tidal perturbations. In case the initial eccentricities of the orbits of the three planets are equal to 0.04, the eccentricities of the orbits of one of the planets K2-72 d or K2-72 e should not exceed 0.03 to ensure the stability of the system. The study was supported by the Russian Ministry of Science and Higher Education via the State Assignment Project FEUZ-2020-0038.

Speaker: Eduard Kuznetsov (Ural Federal University)

122 Impact of Dynamical Tides on Planetary System Stability: Evolution of Multi-Planet Systems

Evolution models of planetary systems find that resonant chains of planets often arise from their formation within protoplanetary disks. However, the occurrence of observed resonant chains, such as the notable TRAPPIST-1 system, is relatively low. This suggests that most of these chains become destabilized after the dissipation of the protoplanetary disk. Stellar tides, particularly the wavelike dynamical tide, have been proposed as potential contributors to the destabilization of resonant chains. The dissipation of the dynamical tide, due to the frequency-dependent tidal excitation of stellar oscillation eigenmodes, potentially accelerates the migration of close-in planets and disrupts the fragile stability of resonant chains. In this study, we investigate the influence of the stellar dynamical tide on multi-planet systems, accounting for its dissipation within the N-body code Posidonius. Notably, this research represents the first exploration of the impact of frequency-dependent dynamical tides on multi-planet systems.

Speaker: Leon Ka-Wang Kwok (Geneva Observatory)

123 The Orbital Eccentricity-Radius Relation for Planets Orbiting M Dwarfs

The orbital eccentricities of exoplanets quantify their current dynamical states and encode information about the predominant processes in their dynamical histories (e.g., the role of giant impacts vs. photoevaporation and core-powered mass loss in sculpting a system's dynamical state). Recent studies have demonstrated a relationship between orbital eccentricity and planet radius, showing modestly elevated eccentricities for large planets and planets in the radius gap, for planets orbiting Sun-like stars. We investigate the eccentricity—radius distribution for planets orbiting M dwarfs, the smallest and most common planet host. We find that large M dwarf planets exhibit elevated eccentricities, similar to FGK-dwarf planets. However, we find a lack of evidence for elevated eccentricities in the radius gap for multi-transit systems. We discuss implications for predominant atmospheric loss mechanisms; namely, supporting evidence for the predominance of photoevaporation as a dynamical sculpting mechanism in M dwarf planets vs. giant impacts in FGK dwarf planets. Furthermore, we situate these findings within an emerging framework of planetary galactic context, as recent work suggests that a planetary system's galactic birthplace, location, and orbit may be intertwined with its current dynamical properties.

Speaker: Sheila Sagear (University of Florida)

Closing Session