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 21121...

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Bibliographic Details
Published in:Astrophysical journal. Letters 2023-09, Vol.954 (1), p.L29
Main Authors: Dichiara, S., Tsang, D., Troja, E., Neill, D., Norris, J. P., Yang, Y.-H.
Format: Article
Language:English
Subjects:
Fluence
Gamma emission
Gamma rays
Gamma-ray bursts
Gravitational wave astronomy
Magnetars
Magnetic fields
Neutron stars
Neutrons
Precursors
Stellar rotation
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Summary: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 (≳10 15 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.
ISSN:2041-8205
2041-8213
DOI:10.3847/2041-8213/acf21d