4th Astro-COLIBRI multi-messenger astrophysics workshop

20 oct. 2025, 09:00 → 24 oct. 2025, 17:00 Europe/Paris

Amphitheater + Cathedrale+ Offices (Institut Pascal)

Fabian Schussler (IRFU / CEA Paris-Saclay), Monica Seglar-Arroyo (IFAE), Patrick Reichherzer (University of Oxford), Ilja Jaroschewski (IRFU / CEA Paris-Saclay), Bernardo Cornejo (IRFU / CEA Paris-Saclay)

The key objective of this workshop is to discuss and develop a research agenda on interconnecting software tools for real-time multi-messenger astronomy. This international workshop provides a forum for leading scientists and young researchers to foster communication between developers and users covering a large range of expertise in the production and use of software tools that make life easier in the rapidly evolving domain of real-time multi-messenger astronomy.

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Funding and support from :

 

lun. 20 octobre ¶

09:00 Arrival at Insitut Pascal

Introduction: Keynotes¶

1 Welcome¶

Orateur: Fabian Schüssler (IRFU / CEA Paris-Saclay)

2 Vera Rubin / LSST¶

Orateur: Bruno Sanchez (CPPM)

3 Astrophysics software development: some perspectives, suggestions, and the write-only documentation phenomenon.¶

Orateur: Phil Evans (Leicester University)

12:30 Buffet lunch

Messengers: GW + Radio¶

4 Latest results from the LVK O4a observing run¶

In this talk, that I will give on behalf of the LVK Collaboration, I will present the latest results from the O4a observing run, placing a special emphasis on the new events in GWTC-4, the multi-messenger and cosmological results obtained.

Orateur: Gergely Dálya (L2IT, Toulouse)

5 Radio variability with ASKAP and LOFAR¶

In this talk, I will discuss the current state of transient studies in the radio domain. With SKA precursor and pathfinder instruments, we are collecting unprecedentedly rich and dense datasets, opening new frontiers in transient astronomy. However, this rapid data influx presents key challenges, particularly in storage and accessibility of light curve data. I will highlight these challenges and explore how radio observations offer unique advantages in identifying and characterizing transients by showing a few compelling examples.

Orateur: Iris de Ruiter (University of Sydney)

6 Radio transients: from LOFAR to SKAO¶

Orateur: Antonia Rowlinson

Messengers: Optical surveys¶

7 ZTF¶

Orateur: Matthew Graham (Caltech)

8 ATLAS¶

Orateur: Heloise Stevance (University of Oxford)

9 The Gravitational-wave Optical Transient Observer (GOTO) project¶

I will present the GOTO project: an array of wife-field survey telescopes principally aimed at following gravitational wave (GW) alerts and performing rapid searches of the localisation areas. The array is situated over two sites, covering Northern and Southern skies, performing an all-sky optical survey, alongside multi-messenger follow up. In addition to GW alerts, GOTO regular reacts to high-energy GRB/X-ray and neutrino alerts, with an in place system to enact automated follow-up and alerting of high confidence candidates, for dissemination to the community.

Orateur: Joseph Lyman (University of Warwick)

10 Small Aperture Telescopes and Multimessenger Follow-Up Networks¶

With the increasing number of high-energy detectors and transient surveys our community is increasingly bottle necked with our ability to perform adequate optical and spectral follow-up observations at scale. In this talk I will discuss the robotization of Manua Kea's oldest telescope, UH88. The system we are building may serve as the foundation for further automation in small/medium aperture telescopes. This in turn, will enable collaboration between facilities in constructing an ad-hoc network for wide coverage transient follow-up.

Orateur: Kyle Hart

15:45 Coffee break

Citizen science: Open Universe¶

https://cern.zoom.us/j/64380403001?pwd=eDFCcC9UTjVTa0d2ZjhIcDJrRVdZQT09

ID de réunion: 643 8040 3001
Code secret: 344296

11 Open Universe¶

Orateur: Ulisses Barres de Almeida (CBPF, Rio de Janeiro)

12 Erasmus Synergies in the Andes and Beyond: Training Multimessenger Astronomers through LA-CoNGA & EL-BONGÓ¶

LA-CoNGA physics (Erasmus+ 2019-23) validated a Bologna-aligned, one-year master's curriculum that merges data science, scientific instrumentation and high-energy physics to modernise graduate education across the Andean region. Eight universities pooled more than 200 open Spanish-language resources and eight remotely operable HEP laboratories via RedCLARA, enabling three cohorts to keep learning seamlessly during the pandemic. The initiative also advanced gender equity, open science practices, and collaborations with CERN, demonstrating that small and medium-sized institutions can excel when they share hardware, software, and teaching expertise.
EL-BONGÓ physics (Erasmus+ 2025-28) scales the concept geographically and disciplinarily. Twelve Central American and Andean partners will weave four Research and learning Communities—High-Energy Physics, Multimessenger Astronomy, Seismology and Earth Hazards, and AI and computational Tools—into a federated Digital Science Hub. FABLabs nurture open-hardware skills, blockchain certificates secure the portability of new 16-hour, 3-ECTS micro-modules, and citizen-science hackathons keep the ecosystem outward-facing.
For Astro-COLIBRI, which disseminates rapid alerts on extreme cosmic phenomena, the synergy is immediate. LA-CoNGA provides a tested pedagogical backbone and culture of reproducibility. At the same time, EL-BONGÓ's multimessenger-astronomy cluster, partnered with the Latin American Giant Observatory, offers real-time data streams, open-source pipelines, and a ready network of early-career scientists. Together, the two Erasmus projects outline a repeatable roadmap for educating, equipping, and connecting the next generation of astronomers who will not only utilise Astro-COLIBRI alerts but also enhance them, fostering a truly borderless, inclusive approach to multi-messenger discovery.

Orateur: Luis Nuñez (Universidad Industrial de Santander)

Astro-COLIBRI¶

https://cern.zoom.us/j/65045162644?pwd=QThndTZkMWZMSENkSHh0bTBlZDVpdz09

ID de réunion: 650 4516 2644
Code secret: 499738

mar. 21 octobre ¶

Contributed talks¶

https://cern.zoom.us/j/67115828357?pwd=UmdwbW0yWHBDOFRjV2NBdjNhd3g2dz09

ID de réunion: 671 1582 8357
Code secret: 258727

13 IceCat-2: Updated IceCube Event Catalog of Alert Tracks¶

This contribution presents preliminary results from IceCat-2, the second public catalog of IceCat Alert Tracks, which plans to build and improve upon the first release, IceCat-1. The initial catalog included all real-time alerts issued since 2016, as well as events observed by IceCube since the start of full-detector data collection in 2011 that would have triggered an alert if the program had been in place at that time. IceCat-2 plans to expand on this by incorporating all additional alerts since IceCat-1, and reprocessing all events with significantly improved reconstruction algorithms. A key advancement in IceCat-2 will come from an updated reconstruction technique introduced by the IceCube Collaboration in September 2024. This approach substantially enhances the angular resolution of muon track alerts, while also improving statistical coverage. With respect to IceCat-1, the 50%(90%) angular uncertainty on track alerts is expected to be reduced by a factor of approximately 5(4). These refined reconstructions allow us to revisit possible correlations between past alerts and sources in gamma-ray and X-ray catalogs. The enhanced precision may uncover new astrophysical associations with known astrophysical sources, offering deeper insight into potential cosmic ray accelerators.

Orateur: Angela Zegarelli (Ruhr Universität Bochum (RUB), Germany)

14 Archival Neutrino Skymaps with SkyLLH: IceCube’s Latest Public Release¶

IceCube has continuously performed all-sky searches for point-like neutrino sources using track-like events. This talk presents a new public data release of astrophysical and atmospheric muon neutrino candidates recorded between April 6, 2008, and May 23, 2022. The dataset includes both through-going and starting muon-induced events reprocessed according to the latest detector calibration while also adding 4 more years of data compared to the previous data release version. It is accompanied by binned detector response functions, enabling sensitive searches for both transient and continuous sources. To support and simplify the use of this data, IceCube provides SkyLLH, an open-source, Python-based modular framework for neutrino source searches. SkyLLH enables users to perform likelihood-based analyses for both transient and continuous emission scenarios across a variety of spectral shapes, leveraging effective areas and detector responses. This talk will provide an overview of the dataset and demonstrate how SkyLLH facilitates its use in multi-messenger and time-domain studies.

Orateur: Chiara Bellenghi

15 Scheduling follow-up observations of energetic transients with the neutrino target scheduler (NuTS)¶

Space missions offer unique opportunities for studying ultra-high-energy (UHE) cosmic rays and neutrinos by leveraging secondary emissions generated by extensive air showers (EAS) resulting from their interactions with the atmosphere or Earth’s crust. Detecting very-high-energy to ultra-high-energy (VHE-UHE) neutrinos associated with transient sources holds great potential for unraveling the origins of UHE cosmic rays and the physical processes driving their production. Stratospheric balloon missions, illustrated recently by the Extreme Universe Space Observatory on a Super Pressure Balloon II Mission (EUSO-SPB2), serve as crucial precursors to space missions. Due to slewing abilities of their telescopes, they can perform follow-up observations of transient sources foreseen as potential candidates for detectable VHE-UHE neutrino emissions. Specialized strategies tailored to stratospheric and space missions are essential for optimizing follow-up observations aimed at detecting these elusive neutrinos for the first time. To address this challenge, we have developed a flexible software dedicated to scheduling transient source observations. The software comprises three main modules: a listener module that aggregates alerts from existing alert systems (e.g., GCN, TNS, ATels) to construct a comprehensive source database, an observability module that factors in the detection system’s properties and trajectory to determine a list of observable sources during a specific timeframe, and a scheduler module that prioritizes observations and proposes an optimized observation schedule. The initial release of the Target of Opportunity (ToO) Scheduler Software is tailored to the requirements of stratospheric balloon missions, with mock observation examples provided for various flight scenarios. This version will be employed for the upcoming PBR flight in 2027. Future developments will extend its capabilities, and ensure its relevance for various types of missions.

Orateur: Claire Guépin-Detrigne (CNRS, LUPM)

16 Peaks and valleys¶

After years studying broadband spectral distributions and trying to constrain theoretical models, a physicist can fall into a valley of scientific frustration. The recent multi messenger events brought a lot of excitement and new energies to face the old and new challenges of this often very abstract field of research. What can we learn from the past multiwalenght efforts and tools and what can we do to ride the multi messenger wave?

Orateur: Marina Manganaro (University of Rijeka, Faculty of Physics)

17 Latency and accuracy of the reconstruction of the gravitational wave signal in Virgo¶

Since Virgo joined the O4 run in April 2024, the h(t) strain signal that may contain any gravitational wave signal has been reconstructed with a 2% accuracy in the 20-2000 Hz frequency band thanks to a good estimation of the interferometer optical response and the construction of accurate models of the mirrors actuators. I will present this h(t) reconstruction and how its current improvements, especially the reduction of its latency down below 2 seconds, may impact the transient detections in the futur O5 run.

Orateur: Didier Verkindt (LAPP-CNRS)

18 The late-time afterglow of GW170817 and implications for jet dynamics¶

GW170817 is the first binary neutron star merger detected with gravitational and electromagnetic waves, and its afterglow is still detectable 7 yr post-merger. Some previous studies of the X-ray afterglow have claimed the onset of a new afterglow component or raised concerns about the data processing techniques. Motivated thus, we present here a reanalysis of X-ray afterglow data for GW170817 and find potential sources of discrepancies between the data reduction techniques employed by various research groups. We also analyse the updated panchromatic afterglow data to find that there is no significant evidence for any new afterglow component (e.g. due to the ejecta that gave rise to the kilonova) and that the jet must be still in a mildly relativistic phase. The decline in the afterglow light curve is significantly shallower compared to that expected from the standard synchrotron afterglow jet models with sideways spreading, indicating either an additional energy injection at late times or the velocity dependence on the microphysics parameters. In this context, we discuss the implications of the late-time afterglow data on jet dynamics.

Orateur: Aman N/A (Indian Institutes of Technology, Kanpur)

10:30 Coffee break

Contributed talks¶

https://cern.zoom.us/j/67115828357?pwd=UmdwbW0yWHBDOFRjV2NBdjNhd3g2dz09

ID de réunion: 671 1582 8357
Code secret: 258727

19 Constraints on Central Engine of Merger-region Gamma-ray bursts¶

The nature of the remnant formed by the coalescence of two neutron stars (NS), is highly sensitive to both the initial mass and the equation of state of the progenitors. Traditionally, accreting black holes formed in the aftermath of NS mergers have been the prevailing central engine model to power short duration gamma-ray bursts (GRBs). However, this framework fails to explain the long-lasting high-energy emission observed in events, such as GRB 211211A and GRB 230307, also accompanied by a candidate kilonova. Their long-lived gamma-ray emission could be explained by considering magnetized NSs as the remnants of such mergers. Late-time radio observations offer an alternative observational window to analyse the GRB central engine. In this presentation, I will discuss how radio studies allow us to discriminate between GRB engine models. This approach enables us to set stringent upper limits on the environment density and ejecta dynamics of this emergent class of transients.

Orateur: Muskan Yadav (University of Rome Tor Vergata)

20 Multi-wavelength Study of Gamma-Ray Burst Afterglows: from X-rays to GeV / TeV¶

Observations of the early X-ray afterglow phases of Gamma-Ray Bursts (GRBs) using the Swift X-ray Telescope (XRT), which operates in the 0.3 to 10 keV energy range, have revealed distinct temporal features beyond those predicted by the standard forward shock afterglow model. Components in the XRT light curve, such as steep decay, flares, and plateaus, suggest more complex afterglow physics. These observations highlight the need for a systematic, multi-wavelength investigation into the temporal and spectral evolution of GRB afterglows. In this work, we perform a comprehensive analysis of GRB afterglow emissions spanning a broad energy interval, from soft X-rays (0.3 keV) to high-energy gamma rays (~ 100 GeV). Our dataset combines observations from Swift/XRT, Swift's Burst Alert Telescope (BAT; 15- 150 keV), and the Fermi Large Area Telescope (LAT), which detects photons in the 30 MeV to 300 GeV range. The selected GRBs in our sample exhibit prominent high-energy gamma-ray components, allowing us to probe the full spectral behavior across this wide range. Our results indicate that the broadband spectra of these GRBs often show a double-peaked structure in their spectral energy distributions. This characteristic provides new insights into the physical processes at play in the emission regions, particularly regarding the emission of X-ray and GeV photons. We interpret these findings in the context of synchrotron self-Compton (SSC) models, discussing how they inform our understanding of the microphysics driving forward shock emissions. Furthermore, our analysis highlights the crucial role of very high energy (VHE) gamma-ray observations (>100 GeV) in uncovering the mechanisms responsible for these complex behaviors. We also explore the future potential of observatories such as the Cherenkov Telescope Array Observatory (CTAO) to enhance our understanding of GRB spectral evolution in the VHE domain. By synthesizing observations across multiple energy bands and emphasizing the contributions from VHE instruments, our work advances the broader goal of understanding the physical processes underlying GRB phenomena.

Orateur: Pawan Tiwari (Gran Sasso Science Institute)

21 Early X-ray emission of short Gamma-Ray Bursts: GRB physics and multi-messenger¶

Accurate modeling of the early X-ray emission in short GRBs is essential for probing the GRB engine, understanding jet physics, and improving electromagnetic follow-up of gravitational wave signals from binary neutron star mergers in the context of multi-messenger astronomy. Thanks to the operation of the Swift satellite over the last 20 years, we now have access to an extensive archive of GRB X-ray observations. The early X-ray light curves often present a bright and steep decay phase, whose physical origin remains poorly understood. In short GRBs, this phase is particularly prominent, as their fainter forward-shock emission, resulting from lower energy release and a less dense circumburst environment compared to long GRBs, makes the steep decay easier to detect. Short GRBs thus offer a unique opportunity to monitor the steep decline for an extended duration, up to 15 minutes. In this talk, I will present our systematic analysis of the early X-ray emission of short GRBs, including both the temporal and spectral evolution. We introduce a new modeling technique that accounts for both the curvature and the intrinsic evolution of the GRB spectrum in Swift/XRT data. For the first time, we fit the synchrotron emission model to the GRB spectra during the steep decay phase, enabling us to track the evolution of the synchrotron cooling frequency and the bolometric flux. Our study reveals a tight correlation between the synchrotron cooling frequency and the isotropic equivalent luminosity. This relation enables us to infer the intrinsic properties of short GRBs and assess the detectability of their early X-ray emission by wide-field X-ray cameras. In particular, our work can help to interpret the nature of some fast X-ray transients detected by Einstein Probe and suggest observational multi-messenger strategies.

Orateur: Annarita Lerardi (Gran Sasso Science Institute)

22 Study of the time delay between star formation and short gamma-ray bursts in a hierarchical Bayesian framework¶

We performed a study of the short gamma-ray burst (sGRB) population using a hierarchical Bayesian framework to constrain the (hyper-)parameters of the population model. We considered both an empirical luminosity function model and a more complex quasi-universal structured jet model of the luminosity distribution of the events across the population. Under the assumption of a compact binary merger origin, we modeled the redshift distribution of the population by convolving the cosmic star formation history with a delay time distribution. In this talk, I will discuss the resulting insights on the sGRB delay time distribution, also highlighting the impact of ill-modeled selection effects.

Orateur: Matteo Pracchia (Université de Liège)

23 Exploring Origin of Ultra-Long Gamma-ray Bursts: Lessons from GRB 221009A¶

The brightest Gamma-ray burst (GRB) ever, GRB 221009A, displays ultra-long GRB (ULGRB) characteristics, with a prompt emission duration exceeding 1000 s. To constrain the origin and central engine of this unique burst, we analyse its prompt and afterglow characteristics and compare them to the established set of similar GRBs. To achieve this, we statistically examine a nearly complete sample of Swift-detected GRBs with measured redshifts. Categorizing the sample to Bronze, Silver, and Gold by fitting a Gaussian function to the log-normal of \tninty duration distribution and considering three sub-samples respectively to 1, 2, and 3 times of the standard deviation to the mean value. GRB 221009A falls into the Gold sub-sample. Our analysis of prompt emission and afterglow characteristics aims to identify trends between the three burst groups. Notably, the Gold sub-sample (a higher likelihood of being ULGRB candidates) suggests a collapsar scenario with a hyper-accreting black hole as a potential central engine, while a few GRBs (GRB 060218, GRB 091024A, and GRB 100316D) in our Gold sub-sample favour a magnetar. Late-time near-IR (NIR) observations from the 3.6 m Devasthal Optical Telescope (DOT) rule out the presence of any bright supernova associated with GRB 221009A in the Gold sub-sample. To further constrain the physical properties of ULGRB progenitors, we employ the tool MESA to simulate the evolution of low-metallicity massive stars with different initial rotations. The outcomes suggest that rotating (Omega > 0.2 Omega_{c) massive stars could potentially be the progenitors of ULGRBs within the considered parameters and initial inputs to MESA

Orateur: Amit Kumar (Aryabhatta Research Institute of Observational Sciences (ARIES))

12:15 Lunch break

Platforms¶

24 GCN¶

25 TNS (tbc)¶

26 European Broker Initiative¶

Orateur: Ken Smith (University of Oxford)

27 TOM toolkit¶

Orateur: Lindy Lindstrom (Las Cumbres Observatory)

28 BHTOM: Sit back and relax - the robots are doing the astronomy job for you¶

I will present BHTOM.space tool for an automated time-domain target coordination. The main feature of BHTOM is that it can automatically send telescope observing requests, accept telescope images, process them and produce science-ready standardised measurements. Everything so you can focus on what is essential.

Orateur: Lukasz Wyrzykowski (University of Warsaw)

15:40 Coffee break

Platforms¶

29 Markarian Multiwavelength Data Center (MMDC): A Platform for Accessing and Modeling Data from Blazar Observations¶

Orateur: Narek Sahakyan (ICRANet Armenia IO)

30 Tilepy¶

Orateur: Monica Seglar Arroyo (IFAE)

31 m4opt¶

Orateur: Weizmann Kiendrébéogo (IRFU / CEA Paris-Saclay)

Citizen science¶

https://cern.zoom.us/j/64380403001?pwd=eDFCcC9UTjVTa0d2ZjhIcDJrRVdZQT09

ID de réunion: 643 8040 3001
Code secret: 344296

32 RAPAS¶

Thanks to the support of Paris Observotory, RAPAS build a french amateur network equiped withe Gaia like filters and with prototypes of spetrograph to deliver photometric monitoring and SED on alerts. We intend to develop on an international scale this network. Therefore we have to implement a pipeline to provide data to the scientific community.

Orateur: Thierry Midavaine (SAF)

33 Verein der Sternenfreunde (Association of German Amateur Astronomers)¶

Orateur: Dominik Elsässer (Universität Dortmund)

34 Pro-Am Commission of the Spanish Astronomical Society¶

Since 2009, the Spanish Astronomy Society (SEA) has maintained a dedicated working group to foster this relationship: the ProAm Commission. This Commission assessed the state of ProAm collaboration in Spain in 2021 and then again in 2023. Data for the reports were gathered from recent amateur astronomy conferences, a thorough review of scientific publications involving amateur astronomers, and two surveys targeting both amateur and professional astronomers. The reports highlighted that Spanish amateur astronomers are actively collaborating with professionals, with approximately 100 amateurs consistently contributing to scientific publications and astronomical circulars. To date, Spanish amateurs have participated in over 200 peer-reviewed articles and nearly 5,000 astronomical circulars. However, the reports also revealed a notable gender disparity: only 4% of professional and 7% of amateur contributors in these collaborations are women. And both amateur and professional communities expressed a need for better communication channels. In this conference, we will review the measures taken by the SEA ProAm Commission during the last years to solve the gender gap and the lack of communication, and to promote new and better ProAm collaborations in Spain.

Orateur: Itziar Garate-Lopez (Universidad del País Vasco / Euskal Herriko Unibertsitatea (UPV/EHU))

Sciathon: introduction¶

https://cern.zoom.us/j/68847741726?pwd=QVBNaDlUSml1Y2MzN21pL0NocUNCZz09

Président de session: Fabian Schüssler (IRFU / CEA Paris-Saclay)

Social events: Beer + chips¶

mer. 22 octobre ¶

Sciathon¶

https://cern.zoom.us/j/68847741726?pwd=QVBNaDlUSml1Y2MzN21pL0NocUNCZz09

12:30 Lunch

Sciathon¶

https://cern.zoom.us/j/68847741726?pwd=QVBNaDlUSml1Y2MzN21pL0NocUNCZz09

jeu. 23 octobre ¶

Sciathon¶

https://cern.zoom.us/j/68847741726?pwd=QVBNaDlUSml1Y2MzN21pL0NocUNCZz09

12:30 Lunch

Sciathon¶

https://cern.zoom.us/j/68847741726?pwd=QVBNaDlUSml1Y2MzN21pL0NocUNCZz09

Social events: Dinner¶

ven. 24 octobre ¶

Sciathon: Project presentations¶

https://cern.zoom.us/j/68847741726?pwd=QVBNaDlUSml1Y2MzN21pL0NocUNCZz09

Sciathon: Conclusion and end of the workshop¶

https://cern.zoom.us/j/68847741726?pwd=QVBNaDlUSml1Y2MzN21pL0NocUNCZz09

12:30 Lunch

Astro-COLIBRI: free discussions + brainstorming¶

https://cern.zoom.us/j/65045162644?pwd=QThndTZkMWZMSENkSHh0bTBlZDVpdz09

ID de réunion: 650 4516 2644
Code secret: 499738