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From γ to Radio: The Electromagnetic Counterpart of GW170817

Nakar, Ehud and Gottlieb, Ore and Piran, Tsvi and Kasliwal, Mansi M. and Hallinan, Gregg W. (2018) From γ to Radio: The Electromagnetic Counterpart of GW170817. Astrophysical Journal, 867 (1). Art. No. 18. ISSN 1538-4357.

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The gravitational waves from the first binary neutron star merger, GW170817, were accompanied by a multiwavelength electromagnetic counterpart, from γ-rays to radio. The accompanying γ-rays seem at first to confirm the association of mergers with short gamma-ray bursts (sGRBs). The common interpretation was that we see an emission from an sGRB jet seen off-axis. However, a closer examination of the subluminous γ-rays and the peculiar radio afterglow was inconsistent with this simple interpretation. Here we present results of 3D and 2D numerical simulations that follow the hydrodynamics and emission of the outflow from a neutron star merger, form its ejection and up to its deceleration by the circum-merger medium. Our results show that the current set of γ-rays, X-rays, and radio observations can be explained by the emission from a mildly relativistic cocoon material (Lorentz factor ~2–5) that was formed while a jet propagated through the material ejected during the merger. The γ-rays are generated when the cocoon breaks out from the engulfing ejecta, while the afterglow is produced by interaction of the cocoon matter with the interstellar medium. The strong early UV/optical signal may be a Lorentz-boosted macronova/kilonova. The fate of the jet itself is currently unknown, but our full-electromagnetic (EM) models define a path to resolving between successful and choked jet scenarios, outputting coupled predictions for the image size, morphology, observed time-dependent polarization, and light-curve behavior from radio to X-ray. The predictive power of these models will prove key in interpreting the ongoing multifaceted observations of this unprecedented event.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Nakar, Ehud0000-0002-4534-7089
Gottlieb, Ore0000-0003-3115-2456
Piran, Tsvi0000-0002-7964-5420
Kasliwal, Mansi M.0000-0002-5619-4938
Hallinan, Gregg W.0000-0002-7083-4049
Additional Information:© 2018 The American Astronomical Society. Received 2018 March 23; revised 2018 August 31; accepted 2018 September 11; published 2018 October 25. This research was supported by the I-Core center of excellence of the CHE-ISF. O.G. and E.N. were partially supported by an ERC starting grant (GRB/SN) and an ISF grant (1277/13). T.P. was partially supported by an advanced ERC grant TReX and by a grant from the Templeton foundation.
Group:Astronomy Department
Funding AgencyGrant Number
Israel Science Foundation1277/13
European Research Council (ERC)UNSPECIFIED
John Templeton FoundationUNSPECIFIED
Subject Keywords:gamma-ray burst: individual (GRB 170817A) – gravitational waves – stars: neutron
Issue or Number:1
Record Number:CaltechAUTHORS:20181025-105425169
Persistent URL:
Official Citation:Ehud Nakar et al 2018 ApJ 867 18
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90414
Deposited By: Tony Diaz
Deposited On:25 Oct 2018 18:06
Last Modified:09 Mar 2020 13:18

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