Revealing x-ray and gamma ray temporal and spectral similarities in the GRB 190829A afterglow

Abstract

Gamma-ray bursts (GRBs), which are bright flashes of gamma rays from extragalactic sources followed by fading afterglow emission, are associated with stellar core collapse events. We report the detection of very-high-energy (VHE) gamma rays from the afterglow of GRB 190829A, between 4 and 56 hours after the trigger, using the High Energy Stereoscopic System (H.E.S.S.). The low luminosity and redshift of GRB 190829A reduce both internal and external absorption, allowing determination of its intrinsic energy spectrum. Between energies of 0.18 and 3.3 tera–electron volts, this spectrum is described by a power law with photon index of 2.07 ± 0.09, similar to the x-ray spectrum. The x-ray and VHE gamma-ray light curves also show similar decay profiles. These similar characteristics in the x-ray and gamma-ray bands challenge GRB afterglow emission scenarios.

Revisiting the PeVatron candidate MGRO J1908+06 with an updated H.E.S.S. analysis

“…This is an another cross-check and validation of gammapy, a toolset for the future gamma-ray observatories, which has started to be used in H.E.S.S. recently [2,23,24…”

Astro-COLIBRI—The COincidence LIBrary for Real-time Inquiry for Multimessenger Astrophysics

“…The fundamental phenomena giving rise to the high fluence of GRBs are not fully understood. GRBs have now been firmly established as very high-energy (VHE) emitters (Abdalla et al 2019;MAGIC Collaboration et al 2019;Abdalla et al 2021). However, at the same time recent intriguing observational results raise questions on the dominant VHE production mechanism, its duration and evolution over time, the required properties of the progenitor as well as the circumburst environment, the maximum energy reached, and its possible scaling with the jet opening angle, etc.…”

Upper limits on the very high energy emission from GRBs observed by MAGIC

“…According to this criterion, GRB 160821B [10] and GRB 190114C [5] are excluded from this study. Also GRB 190829A [9], detected by H.E.S.S., is not included here in order to have a dedicated study of this GRB. With these exclusions, the number of GRBs followed-up by MAGIC in the above mentioned interval is 47.…”

“…The situation has evolved rapidly in the past few years with the announcement by MAGIC ( [4][5][6][7] ) and H.E.S.S. ( [8,9]) of the detection of four GRBs at energies greater than one hundred GeV. They were followed, more recently, by the announcement of the observation of other GRBs at very high energies, albeit with different significance ( [10,11]).…”