A thousand days after the merger: Continued X-ray emission from GW170817

Journal
Date Issued
2020
Author(s)
Troja, E.
•
van Eerten, H.
•
Zhang, B.
•
Ryan, G.
•
•
•
O'Connor, B.
•
Wieringa, M. H.
•
Cenko, S. B.
•
Sakamoto, T.
DOI
Abstract
Recent observations with the Chandra X-ray telescope continue to detect X-ray emission from the transient GW170817. In a total exposure of 96.6 ks, performed between 2020 March 9 and 16 (935-942 d after the merger), a total of 8 photons are measured at the source position, corresponding to a significance of ≍5σ. Radio monitoring with the Australian Telescope Compact Array (ATCA) shows instead that the source has faded below our detection threshold (<33-= $\mu$ Jy, 3σ). By assuming a constant spectral index of β = 0.585, we derive an unabsorbed X-ray flux of ≍1.4 × 10-15-=erg-=cm-2-=s-1, higher than earlier predictions, yet still consistent with a simple structured jet model. We discuss possible scenarios that could account for prolonged emission in X-rays. The current data set appears consistent both with energy injection by a long-lived central engine and with the onset of a kilonova afterglow, arising from the interaction of the sub-relativistic merger ejecta with the surrounding medium. Long-term monitoring of this source will be essential to test these different models....
Funding(s)
Volume
498
Issue
4
Start page
5643
Uri
Url
Issn Identifier
0035-8711
Rights
open.access
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