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The X-ray counterpart to the gravitational-wave event GW170817
Troja, E.,Piro, L.,van Eerten, H.,Wollaeger, R. T.,Im, M.,Fox, O. D.,Butler, N. R.,Cenko, S. B.,Sakamoto, T.,Fryer, C. L.,Ricci, R.,Lien, A.,Ryan Jr, R. E.,Korobkin, O.,Lee, S.-K.,Burgess, J. M.,Lee, Nature Publishing Group 2017 Nature Vol. No.
A long-standing paradigm in astrophysics is that collisions—or mergers—of two neutron stars form highly relativistic and collimated outflows (jets) that power γ-ray bursts of short (less than two seconds) duration. The observational support for this model, however, is only indirect. A hitherto outstanding prediction is that gravitational-wave events from such mergers should be associated with γ-ray bursts, and that a majority of these bursts should be seen off-axis, that is, they should point away from Earth. Here we report the discovery observations of the X-ray counterpart associated with the gravitational-wave event GW170817. Although the electromagnetic counterpart at optical and infrared frequencies is dominated by the radioactive glow (known as a ‘kilonova’) from freshly synthesized rapid neutron capture (r-process) material in the merger ejecta, observations at X-ray and, later, radio frequencies are consistent with a short γ-ray burst viewed off-axis. Our detection of X-ray emission at a location coincident with the kilonova transient provides the missing observational link between short γ-ray bursts and gravitational waves from neutron-star mergers, and gives independent confirmation of the collimated nature of the γ-ray-burst emission.
Sakamoto, T.,Troja, E.,Aoki, K.,Guiriec, S.,Im, M.,Leloudas, G.,Malesani, D.,Melandri, A.,de Ugarte Postigo, A.,Urata, Y.,Xu, D.,D'Avanzo, P.,Gorosabel, J.,Jeon, Y.,Sá,nchez-Ramí,rez, R.,A IOP Publishing 2013 The Astrophysical journal Vol.766 No.1
<P>We present our successful Chandra program designed to identify, with subarcsecond accuracy, the X-ray afterglow of the short GRB 111117A, which was discovered by Swift and Fermi. Thanks to our rapid target of opportunity request, Chandra clearly detected the X-ray afterglow, though no optical afterglow was found in deep optical observations. The host galaxy was clearly detected in the optical and near-infrared band, with the best photometric redshift of z = 1.31(-0.23)(+0.46) (90% confidence), making it one of the highest known short gamma-ray burst ( GRB) redshifts. Furthermore, we see an offset of 1.0 +/- 0.2 arcsec, which corresponds to 8.4 +/- 1.7 kpc, between the host and the afterglow position. We discuss the importance of using Chandra for obtaining subarcsecond X-ray localizations of short GRB afterglows to study GRB environments.</P>
Distance and Properties of NGC 4993 as the Host Galaxy of the Gravitational-wave Source GW170817
Im, Myungshin,Yoon, Yongmin,Lee, Seong-Kook J.,Lee, Hyung Mok,Kim, Joonho,Lee, Chung-Uk,Kim, Seung-Lee,Troja, Eleonora,Choi, Changsu,Lim, Gu,Ko, Jongwan,Shim, Hyunjin American Astronomical Society 2017 ASTROPHYSICAL JOURNAL LETTERS - Vol.849 No.1
The Environment of the Binary Neutron Star Merger GW170817
Levan, A. J.,Lyman, J. D.,Tanvir, N. R.,Hjorth, J.,Mandel, I.,Stanway, E. R.,Steeghs, D.,Fruchter, A. S.,Troja, E.,Schrøder, S. L.,Wiersema, K.,Bruun, S. H.,Cano, Z.,Cenko, S. B.,Postigo, A. de Ugarte American Astronomical Society 2017 ASTROPHYSICAL JOURNAL LETTERS - Vol.848 No.2