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LOW-Γ JETS from COMPACT STELLAR MERGERS: CANDIDATE ELECTROMAGNETIC COUNTERPARTS to GRAVITATIONAL WAVE SOURCES

Lamb, GP and Kobayashi, S (2016) LOW-Γ JETS from COMPACT STELLAR MERGERS: CANDIDATE ELECTROMAGNETIC COUNTERPARTS to GRAVITATIONAL WAVE SOURCES. Astrophysical Journal, 829 (2). ISSN 0004-637X

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Abstract

The American Astronomical Society. All rights reserved.Short gamma-ray bursts (GRBs) are believed to be produced by relativistic jets from mergers of neutron stars (NSs) or NSs and black-holes (BHs). If the Lorentz-factors Γ of jets from compact stellar mergers follow a similar power-law distribution to those observed for other high-energy astrophysical phenomena (e.g., blazars, active galactic nuclei), the population of jets should be dominated by low-Γ outflows. These jets will not produce prompt gamma-rays, but jet energy will be released as X-ray/optical/radio transients when they collide with the ambient medium. Using Monte Carlo simulations, we study the properties of such transients. Approximately 78% of merger jets Mpc result in failed GRBs if the jet Γ follows a power-law distribution of index -1.75. X-ray/optical transients from failed GRBs will have broad distributions of their characteristics: light-curves peak tp ∼ 0.1-10 days after a merger; flux peaks for X-ray 10-6 mJy ≲ Fx ≲ 10-2 mJy; and optical flux peaks at 14 ≲ mg ≲ 22. X-ray transients are detectable by Swift XRT, and ∼85% of optical transients will be detectable by telescopes with limiting magnitude mg ≳ 21, for well localized sources on the sky. X-ray/optical transients are followed by radio transients with peak times narrowly clustered around tp ∼ 10 days, and peak flux of ∼10-100 mJy at 10 GHz and ∼0.1 mJy at 150 MHz. By considering the all-sky rate of short GRBs within the LIGO/Virgo range, the rate of on-axis orphan afterglows from failed GRBs should be 2.6(26) per year for NS-NS(NS-BH) mergers, respectively. Since merger jets from gravitational-wave (GW) trigger events tend to be directed to us, a significant fraction of GW events could be associated with the on-axis orphan afterglow.

Item Type: Article
Uncontrolled Keywords: 0201 Astronomical And Space Sciences, 0305 Organic Chemistry, 0306 Physical Chemistry (Incl. Structural)
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: American Astronomical Society and IOP Publishing
Date Deposited: 07 Aug 2017 09:55
Last Modified: 07 Aug 2017 09:55
DOI or Identification number: 10.3847/0004-637X/829/2/112
URI: http://researchonline.ljmu.ac.uk/id/eprint/6784

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