arXiv subjects

Fabian Schüssler

Publications and source records attributed to Fabian Schüssler.

At least 19 recordsLinked to original sources

arXiv2026

AI-Assisted Extraction of Follow-up Observations from GCN Circulars in Astro-COLIBRI

We present a new Astro-COLIBRI component that converts free-text GCN Circulars into structured, event-linked follow-up records and combines them with structured reports submitted directly by the community. A continuously running Circular listener associates new reports with transient events, applies deterministic pre-analysis, and invokes a schema-constrained large language model extraction step for photometry, contacts, redshifts, and other reported results and metadata. The resulting records are submitted to the Astro-COLIBRI API, normalized into a common event-level follow-up database, and exposed through the web and mobile interfaces as report summaries, contact tools, optical-afterglow context figures, and downloadable CSV or VOTable products. After tuning, all 1,775 Circulars of an operational evaluation corpus covering the first half of 2026 completed the workflow without failures. An internal human audit of 210 Circulars confirmed 25,827 of 25,880 definite field-level decisions (99.80%), with the remaining errors confined to observation timing and facility attribution in eight of 231 assessed reports. Extracted redshifts agree with the independent GRBweb compilation for 228 of the 249 events the two share, and every disagreement traces to a limit, a candidate-host estimate, or a value later refined rather than to a misread Circular. The final pipeline was applied to the full GCN archive since 2016, yielding 68,393 individual observations from 26,811 reports across 5,787 transient events, and is now running in real time on new Circulars. The reusable parsing and normalization pipeline is released as the open-source Python package astro-colibri-circular-parser. This paper describes the scientific motivation, architecture, extraction schema, quality-control safeguards, user-facing products, and current use-cases of the system.

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arXiv2026

NMMA-Astro-COLIBRI: An Automated Light-Curve Supernovae Classification Service in the Multi-Survey Era

The surge in publicly available photometric alerts from wide-field surveys requires automated tools for real-time transient classification. We present NMMA--Astro-COLIBRI, an on-demand Bayesian classification service that couples the Nuclear-physics and Multi-Messenger Astrophysics (NMMA) inference framework to the Astro-COLIBRI real-time multi-messenger platform. After the detection of an optical transient, if photometry is available, it is quality-filtered. The filtered photometry is fitted by nested sampling against a user-selected model from a library of eleven supernova templates; results are delivered to every user within minutes. Applying two or more models on the same optical transient, the service reports the corresponding log Bayes factors as a quantitative ranking of competing subtypes. We demonstrate the workflow on SN 2021ugl (ZTF21abotose), a Type IIb supernova initially mistaken for a kilonova candidate by automated real-time pipelines, comparing competing supernova and kilonova models. In an early-time configuration using only the first ~ 6 days of photometry in two bands (ZTF g and r), so ten days before spectroscopic confirmation, the empirical Type IIb template recovers the correct classification, favored over both the kilonova template and the kilonova-mimicking shock-cooling model. In the full 47-day, three-band baseline, it again achieves the highest evidence over every competing supernova and kilonova template. These results highlight the importance of a comprehensive supernova template library for kilonova discrimination in the multi-survey era.

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arXiv2026

Commensal image plane transient search methods with the SKAO

This chapter outlines the key, state of the art, techniques required to conduct commensal image plane transient searches. Using significant experience and expertise from conducting transient searches with the SKA pathfinders, we have developed efficient fast imaging strategies, automated transient detection pipelines, determined careful filtering techniques to avoid artifacts, and identified the most useful triggered reprocessing tools. Using these strategies, we will be ideally placed to optimally and reliably detect transient sources from commensal image plane transient surveys. The tools and methods presented in this chapter can be used for all SKA-Mid and SKA-Low array deployments from AA* inclusive.

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arXiv2026

Enabling real-time multi-messenger follow-up of transient events with Astro-COLIBRI

Time-domain astrophysics is a rapidly growing field focused on the study of transient phenomena such as Gamma-Ray Bursts (GRBs), Fast Radio Bursts (FRBs), supernovae, novae, and AGN flares. Their characterization increasingly relies on a multi-messenger and multi-wavelength approach, combining gravitational waves, high-energy neutrinos, and electromagnetic observations across the spectrum. Such a coordinated strategy requires efficient information sharing and thus tools capable of rapidly compiling and contextualizing key data for each new event. We present Astro-COLIBRI, a well-established platform designed to meet this challenge. Astro-COLIBRI combines a public RESTful API, real-time databases, and a cloud-based alert system. It continuously listens to multiple alert streams, applies user-defined filters, and places each event in its multi-messenger and multi-wavelength context. Through its user-friendly interfaces, including a web application and mobile apps for iOS and Android, the platform provides clear data visualization as well as concise summaries of key event properties and observing conditions for user-defined locations.

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arXiv2026

A MeerKAT search for persistent radio sources towards twenty-five localised Fast Radio Bursts

The discovery of persistent radio sources (PRSs) associated with repeating fast radio bursts (FRBs) has shed light on the immediate environments and possible progenitors of these FRBs. The confirmed PRSs may support the theory that FRB progenitors are compact central engines, whilst the non-detections suggest diversity of FRB's local environment. We perform a subarcsecond-resolution MeerKAT search at 1.28 GHz on 25 well-localised FRB positions provided by ASKAP and MeerTRAP. We detect 14 radio sources and provide flux upper limits for 12 non-detections (both these numbers include a source that was detected during two epochs of observation, and not detected during one epoch, adding up to 26). One radio source shows variability as seen in flux variations over three epochs of observation. Archival optical data reveal excesses in the direction of 13 detected radio sources. Similarly for four sources in the X-ray band, with one possibly being a high-energy signature of a radio galaxy core. Since we cannot definitively classify our detected radio sources as PRSs, future high-resolution observations with e-MERLIN will be required to resolve the radio emission and pronounce on the presence of compact PRSs associated with the 14 detected sources presented here.

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arXiv2026

tilepy: A Flexible Open-Source Scheduling Engine for Time-Domain and Multi-Messenger Astronomy

The era of multi-messenger astrophysics requires rapid and efficient follow-up of transient events, many of which, such as gravitational waves (GW), gamma-ray bursts (GRB), and high-energy neutrinos, suffer from poor sky localisation. We present tilepy, a Python-based software designed to optimize observation schedules for these events. We here detail the modular architecture of tilepy, which separates high-level scheduling logic from low-level tiling and pointing tools, enabling full adaptability for ground- and space-based observatories. Furthermore, we describe the integration of tilepy into the Astro-COLIBRI platform, providing the community with a user-friendly interface and API for triggering complex observation campaigns in real time.

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arXiv2026

Multi-Messenger Studies with High-Energy Neutrinos and Gamma Rays: The WST Opportunity

The search for the sources of ultra-high-energy cosmic rays (UHECRs) using high-energy neutrinos represents a frontier in high-energy astrophysics. However, a critical bottleneck remains: the ability to rapidly survey the sizable sky areas defined by the localization uncertainties of neutrino detectors and to provide rapid spectroscopic classification of the multitude of optical transients found within them. By deploying a large field-of-view with high-multiplex Multi-Object Spectroscopy (MOS) on a large aperture telescope, one can instantaneously cover neutrino error circles, thus providing crucial spectroscopic classifications of potential counterparts discovered, for example, by the Vera C. Rubin Observatory (LSST) with unprecedented efficiency. Furthermore, simultaneous operation of a giant panoramic central Integral Field Spectrograph (IFS) would allow for detailed kinematic and environmental characterization of primary candidates. This facility would unlock deep synergies between next-generation neutrino telescopes (IceCube-Gen2, KM3NeT) and gamma-ray observatories (CTAO), transforming unique multi-messenger alerts into a comprehensive physical understanding.

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arXiv2026

First Results from the PanRadio Gamma-Ray Burst Collaboration: The 400-day Afterglow of GRB 230815A

We introduce the PanRadio Gamma-ray Burst (GRB) program carried out on the Australia Telescope Compact Array: a systematic, multi-year, radio survey of all southern $\textit{Swift}$ GRB events, comprehensively following the multi-frequency evolution of their afterglows from within an hour to years post-burst. We present the results of the 400-day observing campaign following the afterglow of the long-duration (collapsar) GRB 230815A, the first one detected through this program. Typically, GRB 230815A would not otherwise receive traditional radio follow-up, given it has no known redshift and lacks comprehensive multi-wavelength follow-up due to its high line-of-sight extinction with $A_V=2.3$. We found its early X-ray jet break at ${\sim}0.1$ days post-burst to be at odds with the evolution of the multi-frequency radio light curves that were traced over an unusually long duration of $400$ days. The radio light curves approximately evolved (with minor deviations) according to the standard self-similar expansion for a relativistic blast wave in a homogeneous environment prior to the jet break, showing no evidence for evolutions of the microphysical parameters describing the electron acceleration processes. We reconcile these features by proposing a two-component jet: the early X-ray break originates from a narrow component with a half-opening angle ${\sim}2.1^{\circ}$, while the evolution of the radio afterglow stems from a wider component with a half-opening angle of $\gtrapprox 35^{\circ}$. The PanRadio GRB program will establish a sample of comprehensively followed GRBs, where a rigorous inspection of their microphysical and dynamical parameters can be performed, thereby revealing the diversity of features in their outflows and environments.

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arXiv2025

Spectroscopic Alerts for the Time-Domain Era

Time-domain astronomy is entering an era of unprecedented discovery driven by wide-field, high-cadence surveys such as LSST, Roman, Euclid, SKA, and PLATO. While some of these facilities will generate enormous photometric alert streams, the physical interpretation of variability and transients often requires spectroscopy, which encodes changes in ionisation state, kinematics, and accretion that are inaccessible to photometry alone. A critical gap is therefore emerging: next-generation surveys may produce up to $\sim10^9$ alerts per year, whereas global spectroscopic follow-up is limited to only $\sim10^4$--$10^5$ transient spectra annually. We present the concept of spectroscopic alerts: real-time notifications triggered by significant spectral evolution, enabling spectroscopy to act as a discovery channel rather than solely as follow-up. We outline the key science cases enabled by this capability and describe the instrumental and operational requirements of a wide-field, highly multiplexed spectroscopic facility capable of delivering real-time spectral discovery for 2040s time-domain and multi-messenger astronomy.

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arXiv2025

H.E.S.S. observations of SN 2024ggi

Supernova (SN) explosions interacting with dense circumstellar medium are considered to be very promising sites for efficient cosmic-ray (CR) acceleration and subsequent emission of neutral-pion-decay gamma rays. These environments share similarities with already detected gamma-ray novae, but with much greater available energy content, so it is important to characterize their emission in the very-high-energy range. We present the results of H.E.S.S. observations of one such candidate source - SN 2024ggi, located in NGC 3621 at a distance of 7.24 Mpc. A total of 30 hours of data, gathered throughout a month of post-explosion observations, provide flux upper limits that are used to constrain source parameters, offering meaningful insights for theoretical predictions. We exclude bright gamma-ray emission in the first day after explosion, and later upper limits are consistent with wind densities derived from optical observations.

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arXiv2025

Transient Observations with LST-1: Key Results and Future Prospects

The recent detections of the afterglow phase of long gamma-ray bursts (lGRBs) at very high energies (VHE, >100 GeV) mark a significant advance in astrophysics of transient phenomena, offering deeper insights into the acceleration mechanisms, jet structure, and physical processes driving GRB emission. In the multi-messenger landscape, both high-energy neutrino and gravitational wave detections are providing new insights into the physics of extreme cosmic accelerators and highlighting the need for rapid and broadband follow-up observations. The Large-Sized Telescope (LST-1), the first telescope of the LST array, part of the Cherenkov Telescope Array Observatory (CTAO) North site, is particularly well-suited for real-time, rapid follow-up of transients. In this contribution, we present the latest achievements of the transient observational program with LST-1, which is now in advanced commissioning on La Palma, Canary Islands. We outline the observational strategies in place and describe the dynamic handling of events by the transient handler of LST-1 (e.g., its ability to handle poorly localised events, including gravitational waves, GRBs and neutrinos). We present the key results from transient observation campaigns conducted so far, discuss the lessons learned, and outline the promising prospects for the future LST-1+MAGIC combined transient program with fast response, via a Transient Handler.

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arXiv2025

tilepy: Smart Scheduling for Multi-Messenger Astronomy from Earth to Orbit

The rise of direct detection of gravitational waves (GWs) started a new era in multi-messenger astrophysics. Like GWs, many other astrophysical transient sources suffer from poor localization, which can span tens to thousands of square degrees in the sky. Moreover, as the detection horizon for these transients widens and the detection rate increases, current electromagnetic follow-up facilities require tools to optimize the follow-up of poorly localized events and save valuable telescope time for their time-domain astrophysics programs. We present \texttt{tilepy}, a Python library, and a tool to optimize the follow-up of poorly localized transient events. \texttt{tilepy} is used for GWs as well as other poorly localized events such as gamma-ray bursts detected by Fermi-GBM and neutrino candidates from IceCube. \texttt{tilepy} has also been optimized to integrate smoothly with multiple ground-based observatories operating individually or simultaneously with diverse observational configurations. In this contribution, we introduce the latest developments from \texttt{tilepy}, mainly the ability to operate with space-based observatories while taking into consideration factors such as Earth, Sun, and Moon occultation and South Atlantic Anomaly passage. We present innovations to the platform, handling a variety of field of view shapes, the possibility of optimizing observation scheduling with artificial intelligence tools and examples of its use on transient astrophysical events.

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arXiv2025

Astro-COLIBRI: Empowering Citizen Scientists in Multi-Messenger Astrophysics

In the era of real-time astronomy, citizen scientists play an increasingly important role in the discovery and follow-up of transient astrophysical phenomena. From local astronomical societies to global initiatives, amateur astronomers contribute valuable observational data that complement professional efforts. Astro-COLIBRI facilitates these contributions by providing a user-friendly platform that integrates real-time alerts, data visualization tools, and collaborative features to support astronomers at all levels. The Astro-COLIBRI Citizen Science Program provides engagement opportunities across multiple scales. At the grassroots level, we collaborate with local astronomy clubs, equipping them with accessible tools for transient event monitoring. National and international networks, such as RAPAS in France, leverage Astro-COLIBRI's real-time capabilities for coordinated observations. On a global scale, we actively participate in high-impact citizen science and capacity building initiatives, including the International Astronomical Union (IAU) Citizen Science Program and the "Open Universe" initiative led by the United Nations Office for Outer Space Affairs (UNOOSA). These collaborations enhance the accessibility of real-time astrophysical data and foster inclusive participation in cutting-edge astronomy. In this contribution, we will present the Astro-COLIBRI Citizen Science Program, highlighting its technical framework, community impact, and case studies of successful amateur contributions. We will showcase how our platform facilitates the rapid exchange of information between professional and amateur astronomers, democratizing access to multi-messenger astrophysics and enabling the global community to contribute meaningfully to time-domain discoveries.

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arXiv2025

Astro-COLIBRI: A Comprehensive Platform for Real-Time Multi-Messenger Astrophysics

The detection of transient phenomena such as Gamma-Ray Bursts (GRBs), Fast Radio Bursts (FRBs), stellar flares, novae, and supernovae, alongside novel cosmic messengers like high-energy neutrinos and gravitational waves, has transformed astrophysics in recent years. Maximizing the discovery potential of multi-messenger and multi-wavelength follow-up observations, as well as serendipitous detections, requires a tool that rapidly compiles and contextualizes relevant information for each new event. We present Astro-COLIBRI, an advanced platform designed to meet this challenge. Astro-COLIBRI integrates a public RESTful API, real-time databases, a cloud-based alert system, and user-friendly clients (a website and mobile apps for iOS and Android). It processes astronomical alerts from multiple streams in real time, filtering them based on user-defined criteria and placing them in their multi-wavelength and multi-messenger context. The platform offers intuitive data visualization, a quick summary of relevant event properties, and an assessment of observing conditions at numerous observatories worldwide. We here describe its architecture, data resources, and main functionalities. We highlight the automatic collection of photometric data from a variety of large scale optical surveys, a recently added feature that significantly improves the capabilities of the Astro-COLIBRI platform.

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arXiv2024

Cross-Observatory Coordination with tilepy: A Novel Tool for Observations of Multi-Messenger Transient Events

Time-domain astrophysics has leaped forward with the direct discovery of gravitational waves and the emergence of new generation instruments for multi-messenger studies. The capacity of the multi-messenger multi-wavelength community to effectively pursue follow-up observations is hindered by the suboptimal localization of numerous transient events and the escalating volume of alerts. Thus, we have developed an effective tool to overcome the observational and technical hurdles inherent in the emerging field of multi-messenger astrophysics. We present tilepy, a Python package for the automatic scheduling of follow-up observations of poorly localized transient events. It is ideally suited to tackle the challenge of complex follow-up in mid and small-FoV telescope campaigns, with or without human intervention. We demonstrate the capabilities of tilepy in the realm of multi-observatory, multi-wavelength campaigns, to cover the localization uncertainty region of various events ultimately aiming at pinpointing the source of the multi-messenger emission. The tilepy code is publicly available on GitHub and is sufficiently flexible to be employed either automatically or in a customized manner, tailored to collaboration and individual requirements. tilepy is also accessible via a public API and through the Astro-COLIBRI platform.

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arXiv2024

Astro-COLIBRI: Empowering Citizen Scientists in Time Domain Astronomy

In recent decades, astronomy and astrophysics have experienced several fundamental changes. On one hand, there has been a significant increase in the observation of transient phenomena, which are short-lived events such as supernova explosions, fast radio bursts, and gamma-ray bursts. In addition, the detection of a growing number of different cosmic messengers provides researchers with crucial information about these objects. For example, the detection of high-energy neutrinos and gravitational waves regularly complements traditional astronomical observations in the electromagnetic spectrum. This trend is expected to intensify in the coming years with the commissioning of a wide variety of next-generation observatories, which will enable more in-depth studies of the transient sky. To enhance our understanding and optimize the observations of these phenomena, we have developed the Astro-COLIBRI platform. It is freely available to amateur and professional astronomers in the form of a smartphone application (iOS and Android), a web interface, an API, and a chatbot 'Astro-COLIBRI GPT', among many other features. Astro-COLIBRI serves as a central access point for information on astrophysical sources and transient events, allowing a wide network of observers to track and receive real-time alerts. Here we highlight the key features of Astro-COLIBRI, with a particular emphasis on recent innovations. These include a discussion forum that facilitates user interactions and our strengthened collaboration with various networks of amateur astronomers.

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arXiv2024

Managing the Growing Complexity of Multi-Messenger Transient Events with Astro-COLIBRI

Observations of transient phenomena, such as GRBs, FRBs, novae/supernovae explosions, coupled with the detection of cosmic messengers like high-energy neutrinos and gravitational waves, have transformed astrophysics. Maximizing the discovery potential necessitates tools for swiftly acquiring an overview of the most relevant information for each new detection. Introducing Astro-COLIBRI, a comprehensive platform designed to meet this challenge. Astro-COLIBRI features a public API, real-time databases and alert systems, a discussion forum, and a website and iOS/Android apps as user clients. In real time, it evaluates incoming astronomical observation messages from all available alert streams, filters them based on user-defined criteria, and contextualizes them in the multi-wavelength (MWL) and multi-messenger (MM) context. User clients offer a graphical representation, providing a succinct summary for quick identification of interesting phenomena and assessing observing conditions globally.

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arXiv2024

Chasing Gravitational Waves with the Cherenkov Telescope Array

The detection of gravitational waves from a binary neutron star merger by Advanced LIGO and Advanced Virgo (GW170817), along with the discovery of the electromagnetic counterparts of this gravitational wave event, ushered in a new era of multimessenger astronomy, providing the first direct evidence that BNS mergers are progenitors of short gamma-ray bursts (GRBs). Such events may also produce very-high-energy (VHE, > 100GeV) photons which have yet to be detected in coincidence with a gravitational wave signal. The Cherenkov Telescope Array (CTA) is a next-generation VHE observatory which aims to be indispensable in this search, with an unparalleled sensitivity and ability to slew anywhere on the sky within a few tens of seconds. New observing modes and follow-up strategies are being developed for CTA to rapidly cover localization areas of gravitational wave events that are typically larger than the CTA field of view. This work will evaluate and provide estimations on the expected number of of gravitational wave events that will be observable with CTA, considering both on- and off-axis emission. In addition, we will present and discuss the prospects of potential follow-up strategies with CTA.

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