Abstract
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.
| Original language | English |
|---|---|
| Article number | L57 |
| Journal | Astrophysical Journal Letters |
| Volume | 944 |
| Issue number | 2 |
| DOIs | |
| State | Published - 1 Feb 2023 |
Bibliographical note
Publisher Copyright:© 2023. The Author(s). Published by the American Astronomical Society.
Funding
We thank the anonymous referee for the valuable comments and suggestions. We also thank Damien Bégué, Hüsne Dereli-Bégué, Michael S. Briggs, Xue-Feng Wu, Zi-Gao Dai, Ye-Fei Yuan, Yi-Fu Cai, En-Wei Liang, Remo Ruffini, and ICRANet members for many helpful discussions on GRB physics and phenomena. In particular, L.L. would like to dedicate this piece to the memory of Dr. Magnus Axelsson, a close colleague who passed away recently and was one of its main contributors. A.J.C.-T. acknowledges financial support from the State Agency for Research of the Spanish MCIU, through the “Center of Excellence Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). D.A.K. acknowledges support from Spanish National Research Project RTI2018-098104-J-I00 (GRBPhot). We also acknowledge the use of public data from the Fermi Science Support Center (FSSC) and the UK Swift Science Data Center.
| Funders | Funder number |
|---|---|
| Center of Excellence Severo Ochoa | |
| Fermi Science Support Center | |
| Spanish National Research Project | RTI2018-098104-J-I00 |
| State Agency for Research | |
| Swift Science Data Center | |
| Instituto de Astrofísica de Andalucía | SEV-2017-0709 |