The afterglow and kilonova of the short GRB 160821B

DOI: 
10.1093/mnras/stz2255
Publication date: 
01/10/2019
Main author: 
Troja, E.
IAA authors: 
Castro-Tirado, A. J.;Hu, Y.;Márquez, I.
Authors: 
Troja, E.;Castro-Tirado, A. J.;Becerra González, J.;Hu, Y.;Ryan, G. S.;Cenko, S. B.;Ricci, R.;Novara, G.;Sánchez-Rámirez, R.;Acosta-Pulido, J. A.;Ackley, K. D.;Caballero García, M. D.;Eikenberry, S. S.;Guziy, S.;Jeong, S.;Lien, A. Y.;Márquez, I.;Pandey, S. B.;Park, I. H.;Sakamoto, T.;Tello, J. C.;Sokolov, I. V.;Sokolov, V. V.;Tiengo, A.;Valeev, A. F.;Zhang, B. B.;Veilleux, S.
Journal: 
Monthly Notices of the Royal Astronomical Society
Refereed: 
Yes
Publication type: 
Article
Volume: 
489
Pages: 
2104-2116
Abstract: 
GRB 160821B is a short duration gamma-ray burst (GRB) detected and localized by the Neil Gehrels Swift Observatory in the outskirts of a spiral galaxy at z = 0.1613, at a projected physical offset of 16 kpc from the galaxy's center. We present X-ray, optical/nIR, and radio observations of its counterpart and model them with two distinct components of emission: a standard afterglow, arising from the interaction of the relativistic jet with the surrounding medium, and a kilonova, powered by the radioactive decay of the sub-relativistic ejecta. Broadband modelling of the afterglow data reveals a weak reverse shock propagating backward into the jet, and a likely jet-break at 3.5 d. This is consistent with a structured jet seen slightly off-axis (θ<SUB>view</SUB> ̃ θ<SUB>core</SUB>) while expanding into a low-density medium (n ≈ 10<SUP>-3</SUP> cm<SUP>-3</SUP>). Analysis of the kilonova properties suggests a rapid evolution towards red colours, similar to AT2017gfo, and a low-nIR luminosity, possibly due to the presence of a long-lived neutron star. The global properties of the environment, the inferred low mass (M<SUB>ej</SUB> ≲ 0.006 M<SUB>☉</SUB>) and velocities (v<SUB>ej</SUB> ≳ 0.05c) of lanthanide-rich ejecta are consistent with a binary neutron star merger progenitor.
Database: 
ADS
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85075117114&doi=10.1093%2fmnras%2fstz2255&partnerID=40&md5=d64f029bd3d1d33b85267a5827a4c2e6
ADS Bibcode: 
2019MNRAS.489.2104T
Keywords: 
gravitational waves;nuclear reactions;nucleosynthesis;abundances;gamma-ray burst: general;stars: neutron;Astrophysics - High Energy Astrophysical Phenomena