TY - JOUR

T1 - What determines the structure of short gamma-ray burst jets?

AU - Urrutia, Gerardo

AU - De Colle, Fabio

AU - Murguia-Berthier, Ariadna

AU - Ramirez-Ruiz, Enrico

PY - 2021/5

Y1 - 2021/5

N2 - The discovery of GRB 170817A, the first unambiguous off-axis short gamma-ray burst (sGRB) arising from a neutron star merger, has challenged our understanding of the angular structure of relativistic jets. Studies of the jet propagation usually assume that the jet is ejected from the central engine with a top-hat structure and its final structure, which determines the observed light curve and spectra, is primarily regulated by the interaction with the nearby environment. However, jets are expected to be produced with a structure that is more complex than a simple top-hat, as shown by global accretion simulations. We present numerical simulations of sGRBs launched with a wide range of initial structures, durations, and luminosities. We follow the jet interaction with the merger remnant wind and compute its final structure at distances greater than or similar to 10(11) cm from the central engine. We show that the final jet structure, as well as the resulting afterglow emission, depends strongly on the initial structure of the jet, its luminosity, and duration. While the initial structure of the jet is preserved for long-lasting sGRBs, it is strongly modified for jets barely making their way through the wind. This illustrates the importance of combining the results of global simulations with propagation studies in order to better predict the expected afterglow signatures from neutron star mergers. Structured jets provide a reasonable description of the GRB 170817A afterglow emission with an off-axis angle theta(obs) approximate to 22.5 degrees.

AB - The discovery of GRB 170817A, the first unambiguous off-axis short gamma-ray burst (sGRB) arising from a neutron star merger, has challenged our understanding of the angular structure of relativistic jets. Studies of the jet propagation usually assume that the jet is ejected from the central engine with a top-hat structure and its final structure, which determines the observed light curve and spectra, is primarily regulated by the interaction with the nearby environment. However, jets are expected to be produced with a structure that is more complex than a simple top-hat, as shown by global accretion simulations. We present numerical simulations of sGRBs launched with a wide range of initial structures, durations, and luminosities. We follow the jet interaction with the merger remnant wind and compute its final structure at distances greater than or similar to 10(11) cm from the central engine. We show that the final jet structure, as well as the resulting afterglow emission, depends strongly on the initial structure of the jet, its luminosity, and duration. While the initial structure of the jet is preserved for long-lasting sGRBs, it is strongly modified for jets barely making their way through the wind. This illustrates the importance of combining the results of global simulations with propagation studies in order to better predict the expected afterglow signatures from neutron star mergers. Structured jets provide a reasonable description of the GRB 170817A afterglow emission with an off-axis angle theta(obs) approximate to 22.5 degrees.

KW - radiation mechanisms: non-thermal

KW - relativistic processes

KW - methods: numerical

KW - gamma-ray burst: general

KW - stars: jets

KW - ADAPTIVE MESH REFINEMENT

KW - COMPACT OBJECT MERGERS

KW - MERGING NEUTRON-STARS

KW - NUMERICAL SIMULATIONS

KW - DYNAMICS

KW - AFTERGLOW

KW - DIVERSITY

KW - RADIATION

KW - OUTFLOWS

KW - RADIO

U2 - 10.1093/mnras/stab723

DO - 10.1093/mnras/stab723

M3 - Journal article

VL - 503

SP - 4363

EP - 4371

JO - Royal Astronomical Society. Monthly Notices

JF - Royal Astronomical Society. Monthly Notices

SN - 0035-8711

IS - 3

ER -