Short GRB 160821B: A Reverse Shock, a Refreshed Shock, and a Well-sampled Kilonova

DOI: 
10.3847/1538-4357/ab38bb
Publication date: 
01/09/2019
Main author: 
Lamb, G. P.
IAA authors: 
de Ugarte Postigo, A.;Izzo, L.;Kann, D. A.;Thöne, C. C.
Authors: 
Lamb, G. P.;Tanvir, N. R.;Levan, A. J.;de Ugarte Postigo, A.;Kawaguchi, K.;Corsi, A.;Evans, P. A.;Gompertz, B.;Malesani, D. B.;Page, K. L.;Wiersema, K.;Rosswog, S.;Shibata, M.;Tanaka, M.;van der Horst, A. J.;Cano, Z.;Fynbo, J. P. U.;Fruchter, A. S.;Greiner, J.;Heintz, K. E.;Higgins, A.;Hjorth, J.;Izzo, L.;Jakobsson, P.;Kann, D. A.;O’Brien, P. T.;Perley, D. A.;Pian, E.;Pugliese, G.;Starling, R. L. C.;Thöne, C. C.;Watson, D.;Wijers, R. A. M. J.;Xu, D.
Journal: 
The Astrophysical Journal
Refereed: 
Yes
Publication type: 
Article
Volume: 
883
Pages: 
48
Abstract: 
We report our identification of the optical afterglow and host galaxy of the short-duration gamma-ray burst sGRB 160821B. The spectroscopic redshift of the host is z = 0.162, making it one of the lowest redshift short-duration gamma-ray bursts (sGRBs) identified by Swift. Our intensive follow-up campaign using a range of ground-based facilities as well as Hubble Space Telescope, XMM-Newton, and Swift, shows evidence for a late-time excess of optical and near-infrared emission in addition to a complex afterglow. The afterglow light curve at X-ray frequencies reveals a narrow jet, {θ }<SUB>j</SUB>∼ {1.9}<SUB>-0.03</SUB><SUP>+0.10</SUP> deg, that is refreshed at &gt;1 day post-burst by a slower outflow with significantly more energy than the initial outflow that produced the main GRB. Observations of the 5 GHz radio afterglow shows a reverse shock into a mildly magnetized shell. The optical and near-infrared excess is fainter than AT2017gfo associated with GW170817, and is well explained by a kilonova with dynamic ejecta mass M <SUB>dyn</SUB> = (1.0 ± 0.6) × 10<SUP>−3</SUP> M <SUB>☉</SUB> and a secular (post-merger) ejecta mass with M <SUB>pm</SUB> = (1.0 ± 0.6) × 10<SUP>−2</SUP> M <SUB>☉</SUB>, consistent with a binary neutron star merger resulting in a short-lived massive neutron star. This optical and near-infrared data set provides the best-sampled kilonova light curve without a gravitational wave trigger to date.
Database: 
ADS
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85073068225&doi=10.3847%2f1538-4357%2fab38bb&partnerID=40&md5=bf0036e4e2feae30100bef11519a5696
ADS Bibcode: 
2019ApJ...883...48L
Keywords: 
gamma-ray burst: individual: GRB 160821B;stars: neutron;Astrophysics - High Energy Astrophysical Phenomena