Blackholistic Early Career Scientist Workshop, Nijmegen 2026

27 Jan 2026, 14:00 → 30 Jan 2026, 14:00 Europe/Amsterdam

Tuinzaal (Soeterbeeck Conference Centre,)

The Blackholistic Early Career Scientist Workshop is the first dedicated meeting for junior researchers in the Blackholistic collaboration.

This meeting will take place at the Soeterbeeck Conference Center in Ravenstein near Nijmegen, The Netherlands, between January 27 and 30, 2026.

Registration and abstract submission are now open until the end of Monday, December 8th.

Rationale

The goal of this workshop is to promote collaboration among the early careers scientists - PhD students and postdocs - across the various “BlackHolistic” research groups at the University of Amsterdam, the University of Oxford, the University of Namibia, the University of Turku,  and Radboud University.

During this meeting we will identify our scientific goals and potential “BlackHolistic” projects for the upcoming years. In addition, we aim to learn from each other different tools and techniques used in our research via a series of discussion sessions and tutorials.

Meeting Structure 

The structure of the workshop will consist of:

1. A series of short oral presentations by the PhDs/PDs in attendance, with emphasis not just on their past results but what are their next goals and which questions/problems they are hoping to answer in the next year.

2. 1-2 people are expected to chair each session and specifically write down any new topics and suggestions that arise during the Q&A that will be addressed during the “discussion” sessions of the workshop (more info to come when the final schedule of topics is provided).

3. A discussion session to “refine” the questions we hope to answer (as the examples described in the “scientific rationale”), and to identify each new topic arising from the presentations). In this session we will decide how to divide in subgroups the following day.

4. A day of discussions according to interest/expertise and time to have some hands-on tutorial(s) so PhDs/PDs can learn from each other. Some potential examples: how to make a SED from a GRMHD slice, how to use dynamical imaging techniques, how to handle x-ray variability data, how to use RAPTOR, “BHjets”...

5. A final morning when all the information we have gathered during the workshop will be put together, potential new papers and projects can be defined for the future. Potentially, some senior scientist of our collaboration will be attending this last discussion (online or in person). 

 

Given the nature of the workshop as a face-to-face meeting, physical attendance is expected since we will be splitting into subgroups for discussions and promote collaboration among the PhD/PDs. However for the presentations sessions, Q&A and final day of conclusions joining online can be requested.

Registration

At the bottom of this page you can find a link to the registration form. 1 or 2 weeks after the registration period ends, Radboud University will email the participants the information on how to pay the registration fee via credit card.

The 50 EURO registration fee includes: lunches and coffee breaks for the 4 days of the conference, 2 dinners and social activity.

Accommodations

Once you register we will secure your accommodations at the venue in Soeterbeeck. If you had already pre-registered we already made the reservations for you (check-in January 27, check-out January 30) . Radboud University will directly bill your institution for the accommodation charges during your stay (room+breakfast). 

Local Organizing Committee

Raquel Fraga-Encinas (chair), Renze Oosterhuis, Bram van den Berg.

Any questions about the conference can be directed to: r.fraga@astro.ru.nl

Tuesday 27 January

14:00 → 14:45 Registration & Accommodation Assignment

14:45 → 15:15 Coffee break (provided)

15:15 → 15:45 Introduction: Welcome & Group intros

Convener: Raquel Fraga Encinas (Radboud University)

15:45 → 16:00 Introduction: Scientific Goals, meeting structure

Convener: Raquel Fraga Encinas (Radboud University)

16:00 → 18:00 Session 1 - Jet Physics in AGN: Presentations & QAs

Presentations & QA

Convener: Chair: TBD

16:00 Studying jet properties in nearby active galactic nuclei with multi-wavelength, multi-zone modeling

My work involves developing and applying a physically motivated multi-zone jet model to a variety of low luminosity active galactic nuclei, fitting their radio to X-ray spectral energy distributions to constrain and better understand micro/macro jet physics and particle acceleration, and how it might vary between sources. Building on this, a new analysis pipeline is being developed that couples the jet model directly to X-ray and gamma-ray instrument responses, enabling simultaneous fits to high energy counts spectra and broadband flux measurements, and further implementing bayesian analysis into MWL fitting. This model and pipeline will be utilized to study the VHE emission observed from jetted AGN in conjunction with other wavelengths, to better understand the radiative properties & conditions of jets themselves.

Speaker: Ruby Duncan (University of Amsterdam)

16:21 Lighting up a black hole: phenomenological reconstruction of particle microphysics around a black hole

A key open question in astrophysics is how particles are heated and accelerated in accretion flows and how this shapes observed emission. We present a new method for reconstructing the connection between plasma dynamics and particle acceleration in the accretion flow of the LLAGN M87*, using the 2017 Event Horizon Telescope multi-wavelength campaign as a prototype. Our Bayesian framework constrains a multi-dimensional, parameterized lepton distribution in the accretion disk, capturing a range of heating and acceleration mechanisms without relying on specific sub-grid models. By jointly fitting horizon-scale imaging, polarimetric data, and multi-frequency observations, we obtain quantitative constraints on thermal and non-thermal lepton populations, including energetics, spectral indices, and high-energy cutoffs. These results offer new insights into near-horizon acceleration processes and show that multi-wavelength and polarimetric data are essential for breaking degeneracies between microphysical models. The inferred lepton distributions provide data-driven inputs for PIC simulations and can extend to other LLAGN.

Speaker: RITTICK ROY (UNIVERSITY OF AMSTERDAM)

16:42 How can M87 flare so brightly at TeV energies?

The super-fast (~day), very-high-energy (VHE; >0.1 TeV) photon flares from the nearby active galactic nucleus M87 provide a unique, exciting opportunity to fast-forward our understanding of particle acceleration in jets. Despite 5 detected VHE flares in the last 20 years and extensive multiwavelength (MWL) campaigns, the process and location of these VHE flares in the jet are still not fully understood. I will present a physically motivated model to further unravel this question, with a component of persistent emission from an MHD driven multizone jet (BHJet) in combination with a time-dependent flaring component (AM³). Furthermore, I will give an overview of my plans to tackle this problem from a different perspective, using high-resolution H-AMR GRMHD simulations enhanced with test-particles. Looking ahead, this work is also particularly relevant as a preparation for the confirmed 2-month EHT/MWL/VHE movie campaign in Spring 2026.

Speaker: Marc Klinger-Plaisier (Anton Pannekoek Institute - University of Amsterdam)

17:03 Talk [N/A]

Speaker: Subhrat Praharaj (University of Amsterdam)

17:24 Universality of Energy Extraction from Black Holes

I will review several energy extraction mechanisms (classical and quantum) to facilitate discussions on approaching the Blandford-Znajek process in the future.

Speaker: Michael Florian Wondrak

17:45 Session wrap up & Questions

18:00 → 18:30 Break before dinner

18:30 → 20:00 Dinner at Soeterbeeck (provided)

Wednesday 28 January

09:15 → 09:30 Introduction: Structure & logistics of today

Convener: Raquel Fraga Encinas (Radboud University)

09:30 → 10:45 Session 2: A. Presentations & QAs

Convener: Chair: TBD

09:30 The Homogeneous MeerKAT & Swift XRT Radio:X-ray Plane

The radio:X-ray plane is a valuable tool for probing the connection between core accretion and jet production in X-ray binaries during their hard spectral states. Although this correlation was once thought to be universal – and was extended to active galactic nuclei via a mass term – its universality is now questioned due to numerous ‘outliers’ that deviate from the ‘standard’ relation. To date, large studies of the plane have combined data from multiple telescopes, introducing uncertainties when converting fluxes to a common frequency and accounting for differing telescope systematics. ThunderKAT was a five-year programme monitoring outbursting X-ray binaries with the MeerKAT radio telescope, and ran alongside SwiftKAT, which obtained quasi-simultaneous Swift/XRT observations. Using these data, we have compiled the largest homogeneous radio:X-ray plane for X-ray binaries to date. I will present the results of this study, and discuss what the refined correlation reveals about accretion and jet physics.

Speaker: Justine Crook-Mansour (University of Oxford)

09:49 Calibrating the power of stellar mass black hole jets

Binary systems with a stellar mass black hole accreting from a companion star show bright synchrotron flaring in radio through to the infrared, linked to changes in the accretion properties of the black hole and the launch of powerful transient large scale jets. Despite observations of flaring in ~50 X-ray binary systems over 50+ years, many questions remain about the nature of this behaviour. We present the first comprehensive population analysis of synchrotron flaring from stellar mass black holes. We use an updated analysis framework allowing us in a model independent way to constrain the energy, emitting region size and magnetic field strength of the plasma. Correlations over the population of X-ray binaries with varying black hole mass, spin and accretion rate are investigated. We attempt to constrain the typical bulk velocity of the emitting plasma demonstrating whether or not the flaring from X-ray binaries is from a relativistic jet.

Speaker: Fraser Cowie (University of Oxford)

10:08 What we know about very-high-energy particle acceleration in x-ray binary jets

X-ray binaries have recently emerged as a promising candidate to explain the highest energy cosmic rays. I will present an overview of the existing observational constrains provided by gamma ray telescopes, and introduce ongoing efforts to estimate the cosmic rays luminosity of these systems.

Speaker: Laura Olivera-Nieto (Anton Pannekoek Institute for Astronomy, University of Amsterdam)

10:27 A close correspondence between the low X-ray variability and jet ejections

Accretion states and their relationship with the formation of relativistic jets have long been studied to understand the dynamics of jet-launching events. One focus of such studies has been attempting to confirm the causal connection between changes in the accretion flow and the launching of transient ejecta. While suggestions have been made that particular timing signatures (i.e. Type-B QPOs) correspond to the moment of jet launching, we still do not have definitive evidence for this connection. Our sample study indicates that the drop in X-ray variability can be a more reliable signature of jet launching.

Speaker: Zuobin Zhang

10:45 → 11:15 Coffee break (provided)

11:15 → 12:30 Session 2: B. Presentations & QAs

Convener: Chair: TBD

11:15 Black hole jet Lorentz factors across the mass range

Jets from stellar mass black holes in X-ray binaries (XRBs) and supermassive black holes in active galactic nuclei (AGN) provide distinct opportunities to study the jets of black holes across two different mass regimes with very different selection effects. Historically, the apparent speeds of XRB jets have been observed to be lower than those of AGN, leading to the assumption that stellar mass BHs produce slower jets. We employ novel modelling techniques such as nested sampling and simulation-based inference to obtain credible posteriors for the Lorentz factor parent populations of both samples. Both are best described by a power law distribution $N(\Gamma) \propto N^{b}$. Comparing these samples can give insights into fundamental scaling relations across eight orders of magnitude in black hole mass and further our understanding of jet physics.

Speaker: Clara Lilje (University of Oxford)

11:34 Talk title [n/a]

Speaker: Joana Kramer

11:53 A view into the AGN jets with ALMA polarimetry

The ALMA observatory is unprecedented in terms of high quality polarimetric observations at mm and sub-mm wavelengths. With its ~ 1 arcsecond resolution, ALMA can help us study the large scale (kpc) jets of AGN and possibly even untangle their magnetic field structure. I present brightness and polarization maps of M87 and characterize the key observational aspects of the jet, while at the same time exploring what the predictions of different models can tell us about the underlying physics.

Speaker: Douglas Ferreira Carlos (Universidade de São Paulo)

12:12 Imaging black holes and jets from space

The images of the shadows of M87 and Sgr A*, taken by the Event Horizon Telescope using the technique of very long baseline interferometry (VLBI) at 230 GHz, have opened up a new window into horizon-scale black hole and accretion science. However, ground-based VLBI is hitting fundamental resolution limits due to the limited size of the Earth and atmospheric corruptions at high frequencies. Space-based VLBI is the inevitable next step towards order-of-magnitude resolution improvements in black hole imaging. SHARP is a space-to-space VLBI array that will consist of three satellites in Medium Earth Orbits, attaining a resolution of ~3 micro-arcseconds with a fully filled uv-plane at 690 GHz. SHARP images will provide precision measurements of the black hole spacetime, and test of theories of jet launching. The SHARP Experiment (SHARPEx) will demonstrate the space-to-space VLBI technique and provide images of AGN jets at cm wavelengths with unprecedented resolution and fidelity.

Speaker: Freek Roelofs

12:30 → 13:30 Lunch (provided)

13:30 → 15:00 Session 2: C. Presentations & QAs

Convener: Chair: TBD

13:30 Resolving VLBI data

In this presentation I will explain how we use the open-source package "Resolve" to image VLBI data. Specifically we can use Resolve to dynamically image the sparse radio data observed by the EHT to image SMBH's like Sgr A and M87. I will introduce some changes that we have made to Resolve in order to improve the imaging of dynamical features and to open the path to multi-epoch reconstructions.

Speaker: Bram van den Berg (Radboud University)

13:48 Recovering the Fundamental Plane of Black Hole activity using GRMHD simulations

Accreting black holes span a wide range of regimes, from stellar-mass X-ray binaries to supermassive AGN, and they operate across very different accretion states. These systems are often modeled separately, and a key goal of our work is to test whether a single physical framework can describe these systems across both mass and accretion scales.
The fundamental plane of black hole activity—a correlation between radio and X-ray luminosities in sub-Eddington systems—implies that similar physical processes may operate in XRBs and AGN. To investigate this, we use scale-free GRMHD simulations together with the GRRT code RAPTOR (Bronzwaer et al. 2020) to compute synthetic radio and X-ray luminosities and derive the corresponding correlations.
Early results are promising: the simulations reproduce the expected fundamental-plane trend and show indications of additional dependencies, such as inclination angle. This approach also provides a natural framework to explore potential spin-related effects in future work.

Speaker: renze oosterhuis (Radboud University Nijmegen)

14:06 Painting by Numbers with Picasso: validating a new polarized GRRT code using RAPTOR and IPOLE

General relativistic ray-tracing (GRRT) codes are used to track accretion disk photons back to the observer in order to create a simulated image. For polarized observations, such as those of M87, the GRRT must also track the evolution of the full Stokes parameters. We have developed a new polarized GRRT code, Picasso, building on the previous unpolarized version. To validate the use of this code, we compare it to the other GRRT codes RAPTOR and IPOLE. Using pre-existing snapshots from ten general relativistic magnetohydrodynamics simulations, we have also created a library of images for M87 and derived the resulting image statistics. These include the total flux density, linear polarization fraction, average polarization, and the electric vector position angle. Here, we present the results of this validation, as well as discuss the advantages of this new framework as a tool for fitting and recreating EHT data and observations.

Speaker: Aylecia Lattimer (Anton Pannekoek Institute, University of Amsterdam)

14:24 Single-Dish Calibration Pipelines and VLBI Simulation Studies for Millimetre Astronomy with the Africa Millimetre Telescope

This PhD research develops practical tools for millimetre astronomy, supporting blazar monitoring and evaluating the Africa Millimetre Telescope’s (AMT) role in global VLBI. A core component is a single-dish calibration and analysis pipeline for continuum blazar observations. Using IRAM 30-m test data, key calibration steps (pointing, opacity, elevation-dependent gain, and polarization) are first applied in GILDAS/MIRA and then independently implemented in Python from the underlying calibration equations. The two reductions are compared to validate the pipeline and deliver a transparent, flexible workflow, with new IRAM observations planned for further testing.

In parallel, two VLBI studies assess AMT’s contribution to the EHT. SYMBA imaging simulations test how adding AMT affects array performance and image quality for targets such as M87 and Sgr A. Separately, Monte-Carlo fringe-detectability analyses at 230 GHz combine realistic atmospheric conditions, baseline sensitivity, and measured coherence times to estimate how often AMT baselines achieve reliable high-SNR detections.

Speaker: Hiiko Katjaita (University of Namibia)

14:42 Determining the black hole spin of EHT sources

The Event Horizon Telescope (EHT) has enabled horizon-scale imaging of supermassive black holes. However, constraining black hole spin remains a challenge, despite its importance for testing accretion physics, jet launching, and gravity. Therefore, it is worthwhile to investigate new methods for determining spin, particularly those that make minimal assumptions about the complex astrophysics surrounding the black hole. In this talk, I will present a novel method for constraining spin by utilizing hot spots — localized regions around the black hole that flare up and can appear multiple times in images when the hot spot is bright enough. I will also show some initial work on possible new spin dependencies found in MAD disks using GRMHD simulations.

Speaker: Joost de Kleuver (Radboud University)

15:00 → 15:30 Coffee break (provided)

15:30 → 17:30 Session 3: Discussion: Refine Questions, set tomorrows program

Convener: Chair: TBD

17:30 → 18:00 Break before dinner

18:00 → 19:30 Dinner (provided)

19:30 → 20:00 Travel to Nijmegen

20:00 → 22:00 Social Activity: Ice Skating in Nijmegen

Conveners: Bram van den Berg (Radboud University), renze oosterhuis (Radboud University Nijmegen)

Thursday 29 January

09:15 → 09:30 Introduction: Structure & logistics of the day

Convener: Raquel Fraga Encinas (Radboud University)

09:30 → 10:45 Session 4: A. Group discussions

Convener: Chair: TBD

10:45 → 11:15 Coffee break (provided)

11:15 → 12:30 Session 4: B. Group discussions

12:30 → 13:30 Lunch (provided)

13:30 → 15:00 Session 4: C. Tutorials & Discussion

Convener: Chairs: TBD

15:00 → 15:30 Coffee break (provided)

15:30 → 16:30 Session 4: D. Tutorials + Discussion

16:30 → 17:30 Session 4: Collect & write up a document with all the results from discussions

17:30 → 19:30 Dinner in Ravenstein or Nijmegen (NOT provided)

19:30 → 21:30 Social Activity: in Nimegen TBD

Conveners: Bram van den Berg (Radboud University), renze oosterhuis (Radboud University Nijmegen)

Friday 30 January

09:15 → 09:30 Introduction: Logistics of the final day

Convener: Raquel Fraga Encinas (Radboud University)

09:30 → 10:45 Conclusions: A. Present results from discussions (online presence by senior members possible)

Convener: Chair: TBD

10:45 → 11:15 Coffee break (provided)

11:15 → 12:30 Conclusions: B. Define future projects / papers & meeting wrap up

Convener: Chair: TBD

12:30 → 13:30 Lunch (provided)