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Title: Soft X-ray extended emissions of short gamma-ray bursts as electromagnetic counterparts of compact binary mergers: possible origin and detectability

We investigate the possible origin of extended emissions (EEs) of short gamma-ray bursts with an isotropic energy of ∼10{sup 50-51} erg and a duration of a few 10 s to ∼100 s, based on a compact binary (neutron star (NS)-NS or NS-black hole (BH)) merger scenario. We analyze the evolution of magnetized neutrino-dominated accretion disks of mass ∼0.1 M {sub ☉} around BHs formed after the mergers and estimate the power of relativistic outflows via the Blandford-Znajek (BZ) process. We show that a rotation energy of the BH up to ≳ 10{sup 52} erg can be extracted with an observed timescale of ≳ 30(1 + z) s with a relatively small disk viscosity parameter of α < 0.01. Such a BZ power dissipates by clashing with non-relativistic pre-ejected matter of mass M ∼ 10{sup –(2-4)} M {sub ☉}, and forms a mildly relativistic fireball. We show that the dissipative photospheric emissions from such fireballs are likely in the soft X-ray band (1-10 keV) for M ∼ 10{sup –2} M {sub ☉}, possibly in NS-NS mergers, and in the BAT band (15-150 keV) for M ∼ 10{sup –4} M {sub ☉}, possibly in NS-BH mergers. In the former case, such softmore » EEs can provide a good chance of ∼6 yr{sup −1} (ΔΩ{sub softEE}/4π) (R{sub GW}/40 yr{sup −1}) for simultaneous detections of the gravitational waves with a ∼0.°1 angular resolution by soft X-ray survey facilities like the Wide-Field MAXI. Here, ΔΩ{sub softEE} is the beaming factor of the soft EEs and R{sub GW} is the NS-NS merger rate detectable by the advanced LIGO, the advanced Virgo, and KAGRA.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan)
  2. Department of Astronomy and Astrophysics, Department of Physics, Center for Particle and Gravitational Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)
  3. Yukawa Institute for Theoretical Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan)
  4. Department of Physics and Mathematics, College of Science and Engineering, Aoyama Gakuin University, 5-10-1 Fuchinobe, Chuo-ku, Sagamihara-shi, Kanagawa 252-5258 (Japan)
  5. Department of Physics, Tokyo Insititute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)
Publication Date:
OSTI Identifier:
22370006
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 796; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCRETION DISKS; BINARY STARS; BLACK HOLES; COSMIC GAMMA BURSTS; DETECTION; EMISSION; GRAVITATIONAL WAVES; MASS; NEUTRINOS; NEUTRON STARS; ORIGIN; RELATIVISTIC RANGE; RESOLUTION; ROTATION; SOFT X RADIATION; STAR EVOLUTION