Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

The very high energy view of gamma-ray bursts with the MAGIC telescopes

Alessio Berti, Željka Bošnjak, Alberto Castro-Tirado, Stefano Covino, Susumu Inoue, Francesco Longo, Serena Loporchio, Davide Miceli, Razmik Mirzoyan, Elena Moretti, Lara Nava, Koji Noda, David Paneque, Antonio Stamerra, Yusuke Suda, Kenta Terauchi, Ievgen Vovk, Katsuaki Asano, Satoshi Fukami, Nuria Jordana-Mitjans, Andrea Melandri, Carole Mundell, Michele Palatiello, Manisha Shrestha, Iain Steele

TL;DR

Problem: do GRBs emit in the very-high-energy range and can a single SSC mechanism explain afterglow emission? Approach: MAGIC’s rapid, automated follow-up program combined with broad multi-wavelength observations and forward-shock SSC modeling of detected events. Findings: GRB 190114C (z=0.42) and GRB 201216C (z=1.1) reveal sub-TeV emission consistent with SSC in the afterglow, while a large set of non-detections provides upper limits and insights into selection effects; a universal VHE–X-ray relation remains inconclusive. Impact: demonstrates current IACT capabilities to detect VHE GRB afterglows, informs afterglow physics, and motivates population studies with the forthcoming CTAO.

Abstract

Gamma-ray bursts (GRBs) are one of the main targets for the observations of the MAGIC telescopes. As a result of the effort in improving the sensitivity of the instrument and the automatic follow-up strategy, MAGIC detected two GRBs in the very-high-energy (VHE, $E>100$ GeV) range, namely GRB 190114C and GRB 201216C. In GRB 190114C ($z=0.42$), the data collected by MAGIC revealed a new emission component at sub-TeV energies in the afterglow of the GRB. The very rich multi-wavelength dataset, spanning 17 orders of magnitude in energy, allowed to perform a detailed modelling of the broadband emission. The multi-wavelength data could be modelled within a one-zone synchrotron-self Compton scenario with internal $γ-γ$ absorption, where the model parameters are compatible with those found in previous GRB afterglow studies below GeV energies. Similarly, GRB 201216C broadband emission could be explained using the same model, although the amount of simultaneous multi-wavelength data is reduced with respect to GRB 190114C. In particular, GRB 201216C challenged the current MAGIC detection potential, as its redshift was determined to be $z=1.1$, strongly reducing the observed gamma-ray flux but making it the most distant source detected at VHE. These two detections, accompanied by evidence of VHE emission from a few more GRBs, opened up new questions such as the presence of sub-TeV emission in different classes and phases of GRBs. In this contribution we will present the status of the MAGIC GRB follow-up program, with an highlight on its detected GRBs. Moreover we will show the results on the GRBs observed by MAGIC from 2013 to 2019 with no evidence of VHE emission, in particular for those with simultaneous X-ray observations and redshift $z<2$. We will discuss the implications of these results for GRB physics and the challenges and prospects for future GRB observations with MAGIC.

The very high energy view of gamma-ray bursts with the MAGIC telescopes

TL;DR

Problem: do GRBs emit in the very-high-energy range and can a single SSC mechanism explain afterglow emission? Approach: MAGIC’s rapid, automated follow-up program combined with broad multi-wavelength observations and forward-shock SSC modeling of detected events. Findings: GRB 190114C (z=0.42) and GRB 201216C (z=1.1) reveal sub-TeV emission consistent with SSC in the afterglow, while a large set of non-detections provides upper limits and insights into selection effects; a universal VHE–X-ray relation remains inconclusive. Impact: demonstrates current IACT capabilities to detect VHE GRB afterglows, informs afterglow physics, and motivates population studies with the forthcoming CTAO.

Abstract

Gamma-ray bursts (GRBs) are one of the main targets for the observations of the MAGIC telescopes. As a result of the effort in improving the sensitivity of the instrument and the automatic follow-up strategy, MAGIC detected two GRBs in the very-high-energy (VHE, GeV) range, namely GRB 190114C and GRB 201216C. In GRB 190114C (), the data collected by MAGIC revealed a new emission component at sub-TeV energies in the afterglow of the GRB. The very rich multi-wavelength dataset, spanning 17 orders of magnitude in energy, allowed to perform a detailed modelling of the broadband emission. The multi-wavelength data could be modelled within a one-zone synchrotron-self Compton scenario with internal absorption, where the model parameters are compatible with those found in previous GRB afterglow studies below GeV energies. Similarly, GRB 201216C broadband emission could be explained using the same model, although the amount of simultaneous multi-wavelength data is reduced with respect to GRB 190114C. In particular, GRB 201216C challenged the current MAGIC detection potential, as its redshift was determined to be , strongly reducing the observed gamma-ray flux but making it the most distant source detected at VHE. These two detections, accompanied by evidence of VHE emission from a few more GRBs, opened up new questions such as the presence of sub-TeV emission in different classes and phases of GRBs. In this contribution we will present the status of the MAGIC GRB follow-up program, with an highlight on its detected GRBs. Moreover we will show the results on the GRBs observed by MAGIC from 2013 to 2019 with no evidence of VHE emission, in particular for those with simultaneous X-ray observations and redshift . We will discuss the implications of these results for GRB physics and the challenges and prospects for future GRB observations with MAGIC.

Paper Structure

This paper contains 5 sections, 5 figures.

Table of Contents

  1. Introduction
  2. The MAGIC GRB follow-up program
  3. GRB 190114C and GRB 201216C
  4. Study of non-detected GRBs
  5. Conclusions

Figures (5)

  • Figure 1: Aitoff projection skymap showing the position of the GRBs followed-up by MAGIC until June 2025. Red crosses denote GRBs without a redshift estimation, while blue dots are GRBs with known redshift.
  • Figure 2: GRB 190114C multi-wavelength modeling within the afterglow forward shock scenario, where the MAGIC data is interpreted as SSC emission. Two different time interval are considered. From grb190114c_modelling.
  • Figure 3: Multi-wavelength light curves of GRB 201216C, showing the radio, optical, X-ray, LAT and MAGIC data. The best fit model in the synchrotron - SSC forward shock scenario is shown as solid lines. See grb201216c for details on the model parameters. From grb201216c.
  • Figure 4: Comparison of the MAGIC and CTAO-North array $2\sigma$ sensitivity at 250 GeV (orange and blue dashed lines, respectively) with the observed flux points or ULs for TeV-detected GRBs (empty markers) and the most stringent ULs for the non-detected GRBs by MAGIC (filled markers), as a function of exposure time. From grb_ul_paper.
  • Figure 5: Multi-wavelength lightcurve fro GRB 160625B, showing the X-ray fluxes from Swift-XRT and its average in the MAGIC observational time windows as grey points, the LAT data in red and the MAGIC ULs. The latter are computed assuming two different photon indices and EBL models. The red and green vertical strips denote the MAGIC observational time windows. From grb_ul_paper.