Abstract
Particle acceleration is expected to be different between relativistic and non-relativistic collisionless shocks. We show that electromagnetic counterparts to gravitational waves (GWs), gamma-ray burst (GRB) afterglows, are ideal targets for observing trans-relativistic evolution of accelerated electron distribution because the GWs spot nearby GRBs with off-axis jets, otherwise missed in gamma-ray observations. We find that the relativistic spectral slope begins to change steeply near the peak time of the light curve and approaches the non-relativistic limit in about 10 times the peak time. The trans-relativistic evolution of the afterglow synchrotron spectrum is consistent with GRB 170817A observations within errors, and will be measurable in similar but more distant events at a GW horizon ∼200 Mpc in a denser environment. We roughly estimate that such events represent a fraction of 10-50 per cent of the GRB 170817A-like off-axis short GRBs. We also find that the spectral evolution does not depend on the jet structure if their light curves are similar to each other.
Original language | English |
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Pages (from-to) | 5541–5559 |
Number of pages | 19 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 517 |
Issue number | 4 |
Early online date | 22 Oct 2022 |
DOIs | |
Publication status | Published - 1 Dec 2022 |
Keywords
- gamma-ray bursts
- methods: analytical
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science