Upscattered Cocoon Emission in Short Gamma-Ray Bursts as High-energy Gamma-Ray Counterparts to Gravitational Waves

Shigeo S. Kimura, Kohta Murase, Kunihito Ioka, Shota Kisaka, Ke Fang, Peter Mészáros

Research output: Contribution to journalArticle

Abstract

We investigate prolonged engine activities of short gamma-ray bursts (SGRBs), such as extended and/or plateau emissions, as high-energy gamma-ray counterparts to gravitational waves (GWs). Binary neutron-star mergers lead to relativistic jets and merger ejecta with r-process nucleosynthesis, which are observed as SGRBs and kilonovae/macronovae, respectively. Long-term relativistic jets may be launched by the merger remnant as hinted in X-ray light curves of some SGRBs. The prolonged jets may dissipate their kinetic energy within the radius of the cocoon formed by the jet-ejecta interaction. Then the cocoon supplies seed photons to nonthermal electrons accelerated at the dissipation region, causing high-energy gamma-ray production through the inverse Compton scattering process. We numerically calculate high-energy gamma-ray spectra in such a system using a one-zone and steady-state approximation, and show that GeV-TeV gamma-rays are produced with a duration of 102-105 s. They can be detected by Fermi/LAT or CTA as gamma-ray counterparts to GWs.

Original languageEnglish (US)
Article numberL16
JournalAstrophysical Journal Letters
Volume887
Issue number1
DOIs
StatePublished - Dec 10 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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