Gamma-ray bursts: what do we know today that we did not know 10 years ago?

TL;DR

Over the past decade, significant advances have been made in understanding gamma-ray burst progenitors, jet structures, launching mechanisms, magnetic reconnection, early afterglow behaviors, and high-energy observations, reshaping current models and theories.

Contribution

This paper reviews recent progress in gamma-ray burst physics, highlighting new observational data, theoretical developments, and open questions that define the current state of the field.

Findings

Detection of TeV photons and their debated origins

Polarization measurements providing insights into emission mechanisms

Detection of pair annihilation line in GRB 221009A

Abstract

I discuss here the progress made in the last decade on few of the key open problems in GRB physics. These include: (1) the nature of GRB progenitors, and the outliers found to the collapsar/merger scenarios; (2) Jet structures, whose existence became evident following GRB/GW170817; (3) the great progress made in understanding the GRB jet launching mechanisms, enabled by general-relativistic magneto-hydrodynamic (GR-MHD) codes; (4) recent studies of magnetic reconnection as a valid energy dissipation mechanism; (5) the early afterglow, which may be highly affected by a wind bubble, as well as recent indication that in many GRBs, the Lorentz factor is only a few tens, rather than few hundreds. I highlight some recent observational progress, including major breakthrough in detecting TeV photons and the on-going debate about their origin, polarization measurements, as well as the pair annihilation line recently detected in GRB 221009A, and its implications on the prompt emission physics. I point into some open questions that I anticipate would be at the forefront of GRB research in the next decade.