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A Cosmological Fireball with 16% Gamma-Ray Radiative Efficiency

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posted on 2023-08-10, 12:18 authored by L Li, Y Wang, F Ryde, A Pe’er, B Zhang, S Guiriec, AJ Castro-Tirado, DA Kann, M Axelsson, K Page, P Veres, PN Bhat
Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. How efficiently the jet converts its energy to radiation is a long-standing problem, which is poorly constrained. The standard model invokes a relativistic fireball with a bright photosphere emission component. A definitive diagnosis of GRB radiation components and the measurement of GRB radiative efficiency require prompt emission and afterglow data, with high resolution and wide band coverage in time and energy. Here, we present a comprehensive temporal and spectral analysis of the TeV-emitting bright GRB 190114C. Its fluence is one of the highest for all the GRBs that have been detected so far, which allows us to perform a high-resolution study of the prompt emission spectral properties and their temporal evolutions, down to a timescale of about 0.1 s. We observe that each of the initial pulses has a thermal component contributing ∼20% of the total energy and that the corresponding temperature and inferred Lorentz factor of the photosphere evolve following broken power-law shapes. From the observation of the nonthermal spectra and the light curve, the onset of the afterglow corresponding to the deceleration of the fireball is considered to start at ∼6 s. By incorporating the thermal and nonthermal observations, as well as the photosphere and synchrotron radiative mechanisms, we can directly derive the fireball energy budget with little dependence on hypothetical parameters, measuring a ∼16% radiative efficiency for this GRB. With the fireball energy budget derived, the afterglow microphysics parameters can also be constrained directly from the data.

Funding

SEV-2017-0709

RTI2018-098104-J-I00

History

Citation

Liang Li et al 2023 ApJL 944 L57

Version

  • VoR (Version of Record)

Published in

Astrophysical Journal Letters

Volume

944

Issue

2

Pagination

L57 - L57

Publisher

American Astronomical Society

issn

2041-8205

eissn

2041-8213

Acceptance date

2023-02-06

Copyright date

2023

Available date

2023-08-10

Language

en

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