A Luminous Precursor in the Extremely Bright GRB 230307A
Abstract
GRB 230307A is an extremely bright long-duration GRB with an observed gamma-ray fluence of ≳3 × 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; and a temporally extended and spectrally soft tail. We interpret 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 (≳1015 G) magnetic field should be retained by the progenitor neutron star. Alternatively, in the postmerger scenario, the luminous precursor could point to the formation of a rapidly rotating massive neutron star.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2023
- DOI:
- 10.3847/2041-8213/acf21d
- arXiv:
- arXiv:2307.02996
- Bibcode:
- 2023ApJ...954L..29D
- Keywords:
-
- Gamma-ray bursts;
- Neutron stars;
- Gravitational wave astronomy;
- 629;
- 1108;
- 675;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 9 pages, 5 figures, 2 tables. Accepted for publication in ApJ Letters