2023/07/06 by Dichiara, S., Tsang, D., Troja, E. +3 · 6 citations
#FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · doi:10.48550/arxiv.2307.02996
GRB 230307A is an extremely bright long duration GRB with an observed gamma-ray fluence of \gtrsim3×10-3 erg cm-2 (10-1000 keV), second only to GRB 221009A. Despite its long duration, it is possibly associated with a kilonova, thus resembling the case of GRB 211211A. In analogy with GRB 211211A, we distinguish three phases in the prompt gamma-ray emission of GRB 230307A: an initial short duration, spectrally soft emission; a main long duration, spectrally hard burst; a temporally extended and spectrally soft tail. We intepret the initial soft pulse as a bright precursor to the main burst and compare its properties with models of precursors from compact binary mergers. We find that to explain the brightness of GRB 230307A, a magnetar-like (\gtrsim 1015 G) magnetic field should be retained by the progenitor neutron star. Alternatively, in the post-merger scenario, the luminous precursor could point to the formation of a rapidly rotating massive neutron star.