Transients in Middle Earth

9 Feb 2026, 07:00 → 13 Feb 2026, 19:00 Pacific/Auckland

Rātā / Engineering Core Building (University of Canterbury)

Ryan Ridden (University of Canterbury)

“The world is changed. I feel it in the water. I feel it in the earth. I smell it in the air.”

Join the Transients Group at the University of Canterbury for Transients in Middle Earth, a time-domain astronomy conference between the 9^th to the 13^th of February 2026 held in Ōtautahi (Christchurch), Aotearoa New Zealand. Registration ends on the 1^st of February 2026 NZDT.

This meeting will bring together researchers working on transient and variable phenomena, particularly those using space-based observatories and large survey datasets. Various topics such as supernovae, fast transients, microlensing, and more will be discussed.

The first 2.5 days of the conference will feature invited talks, contributed presentations, and focused discussion sessions. We are planning a half day excursion to Mount Sunday (Edoras) in the middle of the week. The remaining 2 days will be structured as collaborative working time—an opportunity for hands-on group projects, proposal planning, and in-depth scientific exchange with fellow researchers and leading experts.

We additionally invite participants to stay for a second optional co-working week, providing space for extended collaboration before exploring the beautiful South Island.

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We are lighting the beacons - and we welcome you to join us in Middle Earth!

Monday 9 February

1 Registration

2 Introduction

3 Welcome

Supernovae

Talks related to the study of supernovae

4 Constraining Cas A’s Shock Break-Out with IR Echoes

Cassiopeia A is a well-studied supernova remnant and one of the youngest remnants in the Milky Way with the supernova occurring in the late 1600s. First infrared (IR) echoes (Krause et al. 2005) and then scattered light echoes of Cas A were found (Rest 2008), which revealed that the supernova was a type IIb (Krause et al. 2008). Further analysis of the IR echoes showed that the EUV-UV radiation of the shock break-out and/or shock cooling of Cas A was the source of the IR echoes (Dwek and Arendt 2008). With JWST, we have now obtained a set of images which shows an intricate and rich set of previously unseen and unresolved substructure in the Cas A IR echoes. I will present how with this new data set and detailed forward modeling, we are able to get much improved constraints on the physical parameters of the shock break-out and cooling of the Cas A SN.

Speaker: Rodrigo Angulo (Johns Hopkins University)

5 SN 2019vxm: A Shocking Coincidence between Fermi and TESS

Shock breakout and, in some cases, jet-driven high-energy emission are increasingly recognized as key signatures of the earliest phases of core-collapse supernovae, especially in Type IIn systems due to their dense, interaction-dominated circumstellar environments. We present a comprehensive photometric analysis of SN$\,$2019vxm, a long-duration, luminous Type IIn supernova, $M_V^{}=-21.41\pm0.05\;{\rm mag}$, observed from X-ray to near-infrared. SN$\,$2019vxm is the first superluminous supernovae Type IIn to be caught with well-sampled TESS photometric data on the rise and has a convincing coincident X-ray source at the time of first light. The high-cadence TESS light curve captures the early-time rise, which is well described by a broken power law with an index of $n=1.41\pm0.04$, significantly shallower than the canonical $n=2$ behavior. From this, we constrain the time of first light to within $7.2\;\rm hours$. We identify a spatial and temporal coincidence between SN$\,$2019vxm and the X-ray transient GRB191117A, corresponding to a $3.3\sigma$ association confidence. Both the short-duration X-ray event and the lightcurve modeling are consistent with shock breakout into a dense, asymmetric circumstellar medium, indicative of a massive, compact progenitor such as a luminous blue variable transitioning to Wolf-Rayet phase embedded in a clumpy, asymmetric environment.

Speaker: Zachary Lane (University of Canterbury)

10:40 Morning tea

6 The Eye of Sauron in SN2025ngs: A Fast Evolving Interacting Supernova with a Disc-like Circumstellar Medium

Supernovae that interact with nearby circumstellar material shed by the progenitor shortly before the terminal explosion shed light on the late lives of massive stars. These objects are highly heterogeneous, with early observations shedding light on even more diversity. We present SN2025ngs, a nearby interacting supernova in NGC5961. SN2025ngs has a spectroscopic evolution almost mimicking SN1998S, with early and later interaction features. This suggests a re-emerging interaction region as the photosphere recedes. Photometrically, however, SN2025ngs is fainter, and also consistent with a short-plateau light curve. We explore the position of SN2025ngs in the landscape of interacting supernovae, and other short-plateau supernovae, and their hosts. We also present early spectroscopy, where, in high resolution data from a day post-discovery, we find evidence of a circumstellar disk around the progenitor, illustrating the complex environments of these diverse transients.

Speaker: Conor Ransome (Steward Observatory, University of Arizona)

7 SN Eos: A Multiply-Imaged, 30x Magnified SN Near the Epoch of Reionization

On September 1, 2025 the Vast Exploration for Nascent, Unexplored Sources program (VENUS) discovered a multiply-imaged supernova (SN) in JWST imaging of the galaxy cluster, MACS1931 (z~0.35). At the site of the lensed images, contemporaneous VLT/MUSE data show Lyman alpha emission from the host, placing the lensed sytem at a spectroscopic redshift = 5.13. We dub this candidate SN Eos – named after the Titan goddess of dawn. The two images of Eos are magnified by ~30x, are nearly simultaneous given their expected time delays (~hours in the rest frame), and are in excellent agreement with an SN IIP in the plateau phase of its light curve evolution in a low-metallicity environment. We present this discovery and our follow-up data, show that SN Eos offers a true test of whether local, low-metallicity SNe IIP are indeed good high-z analogues, and discuss the unique properties of a highly magnified SN II at z > 5. We emphasize that only through an observatory like JWST, paired with a dedicated lensing survey like VENUS, can we push SN discovery and characterization to the Epoch of Reionization.

Speaker: David Coulter (JHU/STScI)

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12:00 Lunch

Space telescopes

Talks related to space telescopes and their discoveries.

9 The James Webb Space Telescope: Engineering a New Era of Discovery

The James Webb Space Telescope (JWST) is the most complex and sensitive space observatory ever deployed, combining revolutionary engineering with unprecedented scientific capability. With its segmented 6.5-meter primary mirror and suite of infrared instruments, JWST enables observations of the Universe with extraordinary sensitivity and angular resolution. In this talk, I will discuss the key technical innovations that underpin JWST’s performance, as well as the challenges and excitement of on-orbit commissioning. I will also address some of the operational and technical obstacles encountered during the first years of science operations. Finally, I will highlight a selection of scientific results and demonstrate how JWST’s engineering design directly enables these new discoveries.

Speaker: Armin Rest (STScI)

10 Lighting the Beacons of the Early Universe: JWST Insights into Supernova Dust Evolution

Supernovae are the ultimate beacons of the time domain universe, signaling the cataclysmic end of massive stars and acting as the cosmic alchemists that forge the building blocks of galaxies. As the world of astronomy changes through the arrival of large survey datasets and advanced space based observatories, we are finally able to resolve long standing questions regarding the origin and evolution of cosmic dust. Core collapse supernovae are pivotal to this story, serving as the primary architects of the chemical enrichment seen in both the local and distant universe. Leveraging the unparalleled infrared capabilities of the James Webb Space Telescope, our research provides a transformative view of the lifecycle of these explosive transients. This presentation explores the longitudinal evolution of supernova ejecta, tracing the journey from the first emergence of molecular precursors to the formation of massive dust reservoirs decades after the initial explosion. By analyzing high resolution data from the Near Infrared Spectrograph and the Mid Infrared Instrument, we have identified the signatures of carbon monoxide and silicon monoxide during the infancy of dust condensation. These space based observations allow us to penetrate obscured regions and measure substantial dust masses that rival historical benchmarks. By providing critical constraints on progenitor mass loss and ejecta physics, this work contributes to the global effort to understand the variable phenomena that shape our evolving cosmos.

Speaker: Melissa Shahbandeh (Space Telescope Science Institute)

11 The Strongly Lensed Supernova Pantheon As Revealed by JWST

The discovery of the strongly lensed supernova (SN) Refsdal in 2014, and the subsequent measurement of the Hubble constant (H0) from its predicted reappearance, marked a new era in time-delay cosmography. Since 2014, strongly lensed SNe have been discovered at a rate of <1 event per year, but the field has been revolutionized with the arrival of JWST. The Cycle 4 Vast Exploration for Nascent, Unexplored Sources (VENUS) survey has already observed 20 massive galaxy clusters in less than four months, revealing an additional three strongly lensed SNe and thereby increasing the rate of lensed SN discovery by an order of magnitude. SN Ares, the first of these discoveries, is a type II core-collapse SN whose host lies at a redshift of 1.3 and is triply-imaged. Due to the effects of strong lensing, SN Ares is expected to reappear in these other two images on the timescale of decades. Such a long time-delay baseline will lead to an incredibly tight constraint on the measured time delay, which can be leveraged for a precise cosmological inference. The most recently discovered event, SN Athena, is also of a core-collapse origin and was caught as the second of three images to arrive. With an expected time delay of a few years, SN Athena's reappearance will lead to a competitive and independent measure of H0, which is vital to addressing the current tension between the cosmic microwave background and local distance ladder results. Further, the magnification afforded by strong lensing will lead to high signal-to-noise spectrophotometric follow-up, establishing these SNe as the best-studied high-redshift transients to date.

Speaker: Conor Larison (STScI)

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13 Search for r-process signatures in collapsars

Massive stars produce the building blocks of life on Earth, such as carbon and oxygen. However, we still do not understand the physical processes responsible for the production of elements heavier than iron, such as gold, via rapid neutron-capture nucleosynthesis (r-process). The first-ever kilonova associated with the gravitational wave event GW170817 demonstrated that binary neutron star mergers produce heavy elements via rapid r-process nucleosynthesis. However, emerging evidence suggests they cannot be the sole source of this nucleosynthesis. Chemical abundance patterns and evolution history in Milky Way halo stars and dwarf galaxies both suggest a prompt enrichment channel in the early universe, well before the binary neutron stars could merge. This enrichment requires a substantially different type of r-process event. Collapsars, a rapidly rotating massive star that collapses and launches outflows rich in neutrons, are another channel proposed by theoretical works. In this talk, I will present the results of JWST observations of a nearby collapsar SN 2024abup. I will discuss difficulties in separating different line signatures to extract the r-process signatures, and what the future pathways are to solve this problem.

Speaker: Manisha Shrestha

14 Ramping Up the Search for Fast Transients with JWST

Fast infrared transients have not been well explored; however, we now have chance to search this parameter space. With creative analysis techniques, we are using the James Webb Space Telescope (JWST) to search for transients with lifetimes from seconds to minutes. A single exposure from JWST is made up of integrations that are a combination of numerous non-destructive reads. This means that a single full-frame image can be split into a time-series of images with cadences ranging from about 3 seconds to 50 seconds depending on the specified readout pattern. In principle, JWST can then be turned into a fast transient infrared telescope just by looking at its diagnostic images. This method is applicable to all NIRCam and MIRI observations, however, detection capability increases with the length of integration time. I will present the JURASSIC (JWST Up the Ramp Analysis: Searching the Sky for Infrared Cosmic-cataclysms) pipeline and report our search’s initial findings, including previously unidentified asteroids.

Speaker: Jaime Luisi (University of Canterbury)

15:00 Afternoon tea

15 Prospects for detection of fast blue optical transients and supernovae from the Roman Galactic Bulge Time Domain Survey.

The GBTDS is one of the three core community surveys to be undertaken during the first five years after launch of the Nancy Grace Roman Space Telescope. Its primary purpose is the detection of Milky Way exoplants by microlensing and transits. However, the survey cadence and area make it useful for extragalactic science, with the obvious caveats of extinction and stellar crowding in the direction of the Galactic Bulge. I will describe a model for estimating the expected yields of extragalactic transients, and discuss how we might detect such events.

Speaker: Michael Albrow (University of Canterbury)

16 Anchoring Redshift Evolution with a Spectroscopically-Normal Type Ia Supernova at z = 2

The Nancy Grace Roman Space Telescope will provide a revolutionary measurement of evolving dark energy out to z < 3. The accuracy of this measurement is predicated on the assumption that Type Ia supernova (SN Ia) luminosities do not evolve with redshift. If present, SN Ia luminosity evolution is expected to be most detectable in the dark matter–dominated era of the Universe (z > 1.5); its effects becoming more pronounced with increasing redshift. Into the Roman era, JWST will remain the only observatory capable of classifying and characterizing z > 2 SNe via spectroscopy. We present the discovery and classification of SN 2025ogs, a normal-SNe Ia at z = 2.049 +/- 0.007. As an anchor in the dark matter-dominated era, this SN offers a key point of comparison for interpreting future high-redshift SN Ia samples. The multi-band NIRCam light curve indicates a blue color (B - V = −0.28 +/- 0.06 mag) and moderately fast-decline (∆m15(B) = 1.55 +/- 0.15 mag), but within standard cosmology cuts. Standardization of its light curve yields a luminosity distance that is in 1.0-σ agreement with ΛCDM. The NIRSpec spectrum (rest-frame optical) displays all of the hallmark absorption features of a normal SN Ia observed at peak-brightness. We find the color, rest-frame near-ultraviolet properties, and Si II line strengths are all consistent with the moderately fast-decline inferred from the multi-band light curve. Multiple absorption features appear less blueshifted relative to SN Ia from the low-z sample. This could indicate that the ejecta of SN 2025ogs lack the high-velocity components typically observed in low-z SN Ia at higher resolution.

Speaker: Matthew Siebert (Space Telescope Science Institute)

17 Newly Identified Ultraviolet Diversity from HST/STIS Observations of High-Velocity SNe Ia

Despite using Type Ia supernovae (SNe Ia) to precisely measure cosmological parameters, we do not know basic facts about the progenitor systems and explosions. Theory suggests that SN Ia progenitor metallicity is correlated with peak luminosity, but not how quickly it fades, which we use to calibrate the luminosity and measure distances. This effect should lead to an increased Hubble scatter, reducing the precision with which we measure distances. If the mean progenitor metallicity changes with redshift or population, cosmological measurements such as the dark energy equation-of-state parameter and the Hubble constant could be biased. Models also indicate that changing progenitor metallicity will have little effect on the appearance of optical/NIR SN data, but significantly alter UV spectra. The sample of SN Ia with near-peak UV spectra is historically lacking in its representation of high-velocity (HV) SN Ia. Recent HST/STIS observations of HV SN Ia (SN 2021J, SN 2022hrs, and SN 2023gft) have revealed unaccounted trends in UV models that are difficult to disentangle from trends with light-curve shape. I will present these data and discuss their implications for how evolving SN Ia populations with redshift may impact our cosmological distance measurements.

Speaker: Matthew Siebert (Space Telescope Science Institute)

18 Making a Difference (Image): Transforming Euclid into a Transient Discovery Machine Through Cross-Observatory Synergies

Detecting transients requires repeated imaging of the same region of the sky to search for the presence of a new object in the resulting "difference image". With the exception of the Euclid Deep Survey (EDS), there is no planned repeated Euclid imaging. As a result, transient searches will not be feasible in the Euclid Wide Survey (EWS), and the same could true of the Roman High Latitude Wide Area Survey (depending on final implementation details). In the foreseeable future, therefore, the widest IR surveys with sufficient depth to detect rare high-z objects (mAB >= 24 in the near-IR) will be the EDS and Roman High Latitude Time Domain Survey, combining for <= 100 deg^2. While transformative, a larger area is needed to detect the rarest transient phenomena in the Universe. To address this, our program seeks to leverage the EWS to unlock access to rare and powerful high-z transients including pair-instability and Population III SNe, by creating a cross-telescope transient detection pipeline. This will result in the deepest and widest multi-epoch near-IR imaging expected for the foreseeable future, and paves the way to unlocking the potential of a massive Roman−Euclid transient survey that is uniquely sensitive to rare high-z SNe.

Speaker: David Coulter (JHU/STScI)

19 TESSELLATING the dynamic optical sky

In the last seven years TESS has given us a unique window into the dynamic universe. While intended for exoplanet discovery this telescope has observed all variety of transient and variable across the sky. Over its lifetime TESS has imaged the sky at cadences ranging from 30 minutes to just 200 seconds. In this talk I will give an overview of the time domain science possible with TESS, and outline the TESSELLATE pipeline which is conducting a systematic search of TESS full frame images.

Speaker: Ryan Ridden (University of Canterbury)

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Tuesday 10 February

Ground-based

Talks for transient science from ground-based observatories.

22 Flying high in the skies over Antarctica, the story of the GUSTO telescope and its data pipeline.

GUSTO (Galactic/Extragalactic Spectroscopic Terahertz Observatory) is a NASA Mission of Opportunity balloon mission which successfully flew for 55 days in early 2024 high over Antarctica. GUSTO carried out fully sampled large-area observations of two key fine structure lines - [NII] 3P1-3P0 and [CII] 2P3/2-2P1/2 over a 62 square degree area of the galactic plane with a velocity resolution better than 1 km/s. The extensive two-dimensional spectral line images of the Milky Way provided by the GUSTO galactic plane survey provide an extensive database of the structure of the ISM's different phases and how they connect to one another.

As part of GUSTO's science team, and data reduction team, the author has spent the time since then wrangling this large data set, and finding more and ever cleverer ways of extracting signal from the noise. As an added bonus, he'll also share how if you are particularly patient (very patient, i.e. tens of millions of years patient) the gas in this data set could blossom into bright transient feature that would light up the night sky!

Speaker: Chris Martin (Explorative Science Foundation)

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24 Before the Great Eruption of Eta Car Unveiled by a Light Echo

The Great Eruption (GE) of Eta Car in the mid-1800s was a spectacular astronomical event, visible to the naked eye (Smith & Frew 2011). It’s the proto-type of eruptive mass loss, luminous blue variables, and supernova impostors. Prior to the discovery of light echoes, the only observations of Eta Car's historical eruption were visual estimates of its brightness and approximate colors. Light echoes (LEs), reflections of light from transients off of interstellar dust, offer us the opportunity to re-observe Eta Car's eruption with modern instrumentation (Rest et al. 2012). In prior work, this allowed us to obtain spectrophotometric time series from the 3rd historic peak (Prieto et al. 2014) as well as from the plateau phase (Smith et al. 2018a,b), showing that the Great Eruption was unusually red, and had extremely fast ejecta with up to 10,000 km/s. In my talk, I present one echo that shows at least 4 repeating peaks, equally spaced by ~5 years. This light echo is inconsistent with the historic light curve as well as the other light echoes! I show that the most likely scenario is that this echo originates from periodic periastron collisions, well before and leading up to the first documented historical event in 1838.

Speaker: Rodrigo Angulo (Johns Hopkins University)

25 The Deeper, Wider, Faster program - 10 years later

The Deeper, Wider, Faster (DWF) program has grown to coordinate over 100 telescopes located on every continent and in space operating at all wavelengths (radio, mm, IRm optical, UV, X-ray and gamma-ray) and includes particle detectors (and gravitational waves, when operating) to search for and study fast transients (those with millisecond-to-day durations). DWF was developed in 2014 and was the first all-wavelength, multimessenger program - even before the first gravitational waves were detected. The program is large and complex, but has 4 main components (1) coordinated all-wavelength wide-field, fast cadenced observations of the same fields at the same time, (2) real-time (seconds-to-minutes) data processing and transient identification, (3) rapid (minutes later) and conventional 8m-class optical, radio, and high-energy ToO triggers, and (4) later time field and target monitoring for fast transients associated with slower evolving events and early detections of slower evolving events. I will highlight the history, growth, and some science outcomes, along with lessons learned from a decade of DWF.

Speaker: Jeff Cooke (Swinburne University)

26 Scientia ex Machina: The Dark Energy Science Collaboration and the Astro-AI Revolution

We are living through parallel revolutions in time-domain astrophysics and artificial intelligence. Within a year of beginning operations, the Vera C. Rubin Observatory will find more transient sources than all previous surveys combined. We will be able to use these cosmic lighthouses as beacons to map how stellar populations evolve with redshift, how feedback from their deaths impacts their host galaxies, and probe the Hubble tension, dark energy, and beyond GR models. Realizing the promise of Rubin Observatory requires that we develop techniques that can rapidly combine time-series, spectra, images, coincident detections, gravitational wave strain measurements, and strong lensing magnification maps - "multi-modal” data - to discover, characterize and use these transient sources for inference. This need for fast analysis at Rubin Observatory-scale is driving the Dark Energy Science Collaboration (DESC) towards incorporating AI in nearly every stage of our pipelines, and this motivates research into building Foundation AI models for the time-domain sky. I will focus on work at the NSF-Simons AI for the Sky (SkAI) institute to build such a Foundation model - Supernova Explosions Learned by Deep ODE Networks (SELDON) - that is accurately forecasting transient light curve behavior, identifying anomalies, and inferring some of the physical properties of transients from light curves and spectra. And of course, it can still do classification much like literature ML efforts for transients. Finally, I will provide an overview of how DESC is preparing for analysis of early Rubin data, highlighting the extent to which AI methods have now become core components of our analysis, and chart where I think we will have to go in the next few years with the combination of Euclid, Roman, and other ground-based data.

Speaker: Gautham Narayan (University of Illinois at Urbana-Champaign)

27 MALLORN: Simulating LSST Nuclear Transients from Real Observations

The Vera C. Rubin Observatory’s 10-Year Legacy Survey of Space and Time (LSST) is expected to revolutionise time-domain astronomy, with a hundredfold increase in detected transients. For tidal disruption events (TDEs) in particular, this will increase the population of observed objects from ~100 to ~30,000. As TDEs are a relatively recent discovery with a small catalogue of objects, many questions remain: Can we observe intermediate black holes via tidal disruption events? Why do TDEs exhibit an apparent preference for green valley galaxies? How common are repeated tidal disruptions? LSST offers an excellent opportunity to answer these questions.

However, the sheer volume of data and detections that LSST will produce presents an inherent challenge to astronomers. We do not have adequate resources to follow up on every object that LSST will discover, so it will be necessary to prioritise a fraction of the objects.

To assist with maximising LSST’s scientific potential and effectively preparing to handle the vast volume of data it will create, we have developed the Many Artificial LSST Lightcurves based on Observations of Real Nuclear transients (MALLORN) data set. MALLORN consists of over 10,000 simulated LSST lightcurves generated from Zwicky Transient Facility (ZTF) photometry, Gaussian processes, machine learning approaches, SNCosmo SED simulations and the Rubin Survey Simulator. By grounding the simulated lightcurves in real ZTF observations, this approach produces a realistic and representative LSST training set with minimal assumptions about the underlying physics of the lightcurves.

We will show how the MALLORN algorithm can be used to simulate transients in any survey given an observed population from a previous survey, and report on the results of our classification challenge. We will also show how we are using these data sets to design triggering criteria for real transients to follow-up rising transients while rejecting faint AGN.

Note: The acronym MALLORN is a reference to the golden-leaved Mallorn trees of Lothlórien

Speaker: Dylan Magill (Queen's University Belfast)

12:00 Lunch

28 Detecting and analyzing LEO satellite streaks with MUSE

The number of low Earth orbit (LEO) satellites is increasing, and they are having a noticeable impact on the quality of a large range of astronomical data. We use archival data from the Multi Unit Spectrographic Explorer (MUSE) to quantify the effects of satellites on the datacubes. MUSE is an integral field unit (IFU) so it captures a spectrum at every pixel in the field of view. Using the starkiller package we have searched all MUSE quicklook images for spatially resolved satellite streaks and have extracted many satellite spectra from the impacted observations. We have detected satellites in 133 MUSE exposures from this search. We find that LEO satellite spectra are diverse and can be modeled as a solar spectrum with variable levels of atmospheric extinction. Through this process we are able to recover the science targets and build a spectral library for LEO satellites which can be used to inform other spectroscopic surveys. From matching the exposure information to archival satellite positions, we can get spectra of objects from the space race until now.

Speaker: Brayden Leicester (University of Canterbury)

29 The KMTnet Microlensing Survey

I will give an introduction to microlensing and describe the KMTNet survey, a high-cadence photometric survey of the Milky Way Bulge. From this survey, and over the last decade, we have detected ~ 25,000 microlensing events using our telescopes in Siding Spring, CTIO and SAAO. I will discuss observational features of the survey, what we have learned about the Galactic population of cool planets, and projections for the Roman Galactic Bulge Time Domain Survey.

Speaker: Michael Albrow (University of Canterbury)

Theory

Talks on theoretical models and their applications in transient astronomy.

30 Constraining transients with BPASS

Over the last 20 years the Binary Population and Spectral Synthesis code has been used to constrain transients through multiple comparisons between theory and observations. For example, resolved supernova progenitors, long-GRB afterglow properties, resolved and unresolved stellar population at supernova and kilonova sites, synthetic supernova lightcurves, and gravitational wave transient rate and Chirp mass distributions. I will briefly overview these results and present the combined picture that we begin to put together and importantly identify which areas we need to work on more.

Speaker: Jan Eldridge (University of Auckland)

31 BPASS Predictions of Compact Object - Luminous Companion Binaries in the Milky Way

We present a study using the Binary Population and Spectral Synthesis code (BPASS) that predicts the Galactic population of binaries that contain a black hole or neutron star. By incorporating the stellar evolution models from the BPASS suite with a Milky Way analogue galaxy from the Feedback in Realistic Environment (FIRE) simulation suite, we can generate a theoretical population of quiescent compact remnant binaries as well as x-ray binaries within our Galaxy. We split the population into quiescent systems before and after their binary interactions, to investigate how such systems evolve and to further understand their role as supernovae remnants. Furthermore, we explore the code’s output of x-ray binaries with a focus on how they can be studied as transients for systems that appear to be quiescent. We predict the distribution of masses and orbital periods for these systems and compare these to the current observed distributions within our Galaxy, including the recently discovered Gaia Black Hole systems. The remnant masses produced by the code for the pre-interaction systems serve to give us the most accurate measurement of the masses for compact remnants that form from supernovae. We find that the agreement in general is reasonable but there are strong indications that we need to include new physical processes within BPASS to be able to accurately reproduce the observed compact remnant distributions. Additionally, we present theoretical yields of these quiescent systems from Gaia DR5 a well as the upcoming Roman Space Telescope."

Speaker: Ms Erin Eastep (University of Auckland)

32 Fast Radio Bursts and Interstellar Objects

Fast radio bursts (FRBs) are transient radio events with millisecond-scale durations and debated origins.
Collisions between planetesimals and neutron stars are one proposed mechanism to produce FRB-like signals, with the planetesimal's strength, size and density determining the time duration and energy of the resulting event. One under-explored source of these planetesimals is the free-floating population of interstellar objects, expected to be extremely abundant in galaxies across the Universe as ubiquitous products of planetary formation.
We investigate ISO-neutron star collisions as a source of FRBs, and predict that the collision rate is comparable with the observed FRB event rate. Using a model linking the properties of planetesimals and the FRBs they produce, we further show that observed FRB durations are consistent with the sizes of known ISOs, and the FRB energy distribution is consistent with the observed size distributions of Solar System planetesimal populations. Finally, we argue that the rate of ISO-neutron star collisions must increase with cosmic time, matching the observed evolution of the FRB rate. Thus, ISO-neutron star collisions are a feasible origin of FRBs.

Speaker: Matthew Hopkins (University of Canterbury)

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15:00 Afternoon tea

Radio

Talks on transients observed by radio telescopes

34 Exploring the Dynamic Radio Sky

The radio sky is highly dynamic, hosting transient and variable sources on timescales from milliseconds to years. In this talk, I will present an overview of the work of the Sydney Radio Transients Group, focusing on the discovery and characterisation of radio transients across a wide range of timescales. Our science spans fast radio bursts, radio afterglows of gravitational-wave events, and longer-lived variable and transient sources.
Much of this work is carried out using the Variables and Slow Transients (VAST) survey with ASKAP, which combines wide-field coverage and high cadence to systematically explore the transient radio sky. I will outline the VAST survey strategy and highlight key results and discoveries, demonstrating how large-scale radio surveys are transforming our understanding of transient and variable radio populations in the era of multi-messenger astronomy. I will also present my research on fast radio bursts, focusing on their detection, characterisation, and what they reveal about their extreme environments.

Speaker: Kavya Shaji (University of Sydney)

35 The CRAFT survey of Fast Radio Bursts and their Host Galaxies

Fast radio bursts (FRBs) are energetic pulses of radio emission typically lasting a few milliseconds, which encode in their telltale parabolic sweeps in time and frequency a fossil record of their passage through ionised gas between and within galaxies. The Commensal Real-time ASKAP Fast Transients (CRAFT) survey was the first to localise a non-repeating FRB to sub-arcsecond precision, and has now pinpointed more than 50 FRBs not just to, but within their host galaxies. Deep imaging with FORS2 and spectroscopy with X-shooter on the VLT of these host galaxies has given us insight into the likely progenitors of FRBs, and demonstrated their potential as cosmological probes. I will present the results of our ESO Large Programme "FURBY", and preview the exciting future for FRB research in the era of the SKA and ELT.

Speaker: Stuart Ryder (Macquarie University)

36 Investigating the Hidden Origins of Fast Radio Bursts and Other Radio Transients

The last decade of investigations into the extragalactic radio sky has led to a paradigm shift, with all-together new and uncharacterized populations of radio transients emerging for the first time. Upgrades in multiple fast radio burst (FRB) experiments have led to the first samples of precisely localized events, enabling host galaxy associations and detailed observations of the immediate environments surrounding FRBs. Such observations play a key role in elucidating the stellar populations that give rise to FRB progenitors. In this talk, I will review our current knowledge of FRB progenitors based on the properties of a small, but growing sample of host galaxies, and I will outline major follow-up efforts to build the first statistically meaningful sample of FRB hosts. I will highlight our recent discovery of an FRB in an unexpected environment, which challenges our previous understanding of these events. Finally, I will explore how the localization of several repeating FRBs in dwarf galaxies, their spatial coincidence with persistent radio sources, and the detection of long-lived radio transients in dwarf galaxies further implicate an entirely new population of radio sources on the sky. I will discuss our large-scale effort to uncover this unique population for the first time.

Speaker: Tarraneh Eftekhari (Northwestern University)

37 Can We Search for Slow Transients with CHORD?

The Canadian Hydrogen Observatory and Radio Transient Detector (CHORD), currently under construction, is the successor to the highly successful CHIME array, and is a flagship project of Canadian radio astronomy. Though not an original design goal, CHIME was found to be an immensely capable detector of Fast Radio Bursts, and CHORD may have unforeseen capabilities in the same spirit, as a detector of transient phenomena on day to year timescales, including TDEs, GRBs, AGN flares and more. I will present the early outcomes of my research, where I am evaluating CHORD as a detector of slow transients by combining detailed simulations and theory. I will cover the powerful advantages offered by CHORD due to its drift-scan nature, large field of view and excellent electronics, as well as the significant difficulties posed by the regular array design and how I have tried to overcome them using various image processing techniques. I will talk about the detailed imaging simulation pipeline used, which includes radiometer noise, AGN and SFGs with realistic distributions, intrinsic and extrinsic source variation, and realistic transients simulated using Redback. The potential future of CHORD for this purpose, including the ability to monitor the location of many known optical transients and the implications of an expanded CHORD array are discussed.

Speaker: Joshua Goodeve (McGill University)

38 Conference dinner

Wednesday 11 February

Future programmes

Session for future instruments and observing programmes

39 The Keck Wide-Field Imager - the future of transient astronomy

The Keck Wide-Field Imager (KWFI) is a 1 degree UV-optimised optical prime focus imager for the Keck telescopes. KWFI will fill several large wide-field imaging capability gaps that exist now and will will be critically needed with the recent and upcoming billion-dollar 'mega-facilities' operating at all wavelengths and messengers. For example, KWFI will provide very deep (m ~ 28-30) wide-field u-band imaging capability, fast readout and filter change (~10 seconds each), ToO capability for all types of transients, 5 broadband, 20 narrowband, and 20 medium-band filters, and a multiplexing mode that includes ~2-minute image reduction and source identifications and a deployable secondary mirror to enable deep Keck optical or IR spectroscopy minutes after the KWFI images are acquired. I will discuss the KWFI design, touch on some science cases, and end with the current status of the instrument.

Speaker: Jeff Cooke (Swinburne University)

40 Ringing in Transients: Future Plans for Global Transient Networks

I will review plans for global transient and detection networks of the future. The BRICS+ astronomy flagship programme entitled the BRICS Intelligent Telescope and Data Network (BITDN) aims to harness existing and future facilities within BRICS+ countries for automated transient observation. Likewise a smaller Africa initiative, the African Integrated Observation Network (AIOS) has similar aims, utilizing continental facilities in northern, eastern and southern Africa. The major next development in transient and variable objectdetections will inevitably push to higher cadences and better sky coverage, as envisaged with GOTTA: a Global Open Transient Telescope Array, a new Chinese-led project. The current concept consists of 135 1-m modified Schmidt telescopes, each with a 25 sq degree field of view and with an effective 18k x 18k CMOS detector and with one dedicated filter (e.g. g, r or i). Ideally, these telescopes will be situated in groups of 3 in both hemispheres and with sufficient longitude range to achieve all-sky coverage, with a cadence of less than an hour. Larger aperture (2-4-m class) telescope will be used for spectroscopic followup.

Speaker: David Buckley (South African Astronomical Observatory)

Excursion

Conference excursion to Mt Sunday

Thursday 12 February

Collaboration: Day 1

41 Public lecture

Friday 13 February

Collaboration: Day 2