The limited contribution of low- and high-luminosity gamma-ray bursts to ultra-high-energy cosmic rays

Samuelsson, Filip; Bégué, Damien; Ryde, Felix; Pe’er, Asaf

The limited contribution of low- and high-luminosity gamma-ray bursts to ultra-high-energy cosmic rays

Files

Samuelsson_2019_ApJ_876_93.pdf(3.67 MB)

Published Version

Date

2019-05-08

Authors

Samuelsson, Filip

Bégué, Damien

Ryde, Felix

Pe’er, Asaf

Publisher

Institute of Physics Publishing

Published Version

10.3847/1538-4357/ab153c

Abstract

The acceleration site for ultra-high-energy cosmic rays (UHECRs) is still an open question despite extended research. In this paper, we reconsider the prompt phase of gamma-ray bursts (GRBs) as a possible candidate for this acceleration and constrain the maximum proton energy in optically thin synchrotron and photospheric models, using properties of the prompt photon spectra. We find that neither of the models favors acceleration of protons to 1020 eV in high-luminosity bursts. We repeat the calculations for low-luminosity GRBs (llGRBs) considering both protons and completely stripped iron and find that the highest obtainable energies are <1019 eV and <1020 eV for protons and iron respectively, regardless of the model. We conclude therefore that for our fiducial parameters, GRBs, including low-luminosity bursts, contribute little to nothing to the UHECRs observed. We further constrain the conditions necessary for an association between UHECRs and llGRBs and find that iron can be accelerated to 1020 eV in photospheric models, given very efficient acceleration and/or a small fractional energy given to a small fraction of accelerated electrons. This will necessarily result in high prompt optical fluxes, and the detection of such a signal could therefore be an indication of successful UHECR acceleration at the source.

Keywords

Gamma-ray burst , General , Cosmic rays

Citation

Samuelsson, F., Bégué, D., Ryde, F. and Pe’er, A. (2019) 'The Limited Contribution of Low- and High-luminosity Gamma-Ray Bursts to Ultra-high-energy Cosmic Rays', The Astrophysical Journal, 876(2), 93. (17pp.) DOI: 10.3847/1538-4357/ab153c