A year in the life of GW 170817: the rise and fall of a structured jet from a binary neutron star merger
Date Issued
2019
Author(s)
Troja, E.
•
van Eerten, H.
•
Ryan, G.
•
•
Burgess, J. M.
•
Wieringa, M. H.
•
•
Cenko, S. B.
•
Sakamoto, T.
Abstract
We present the results of our year-long afterglow monitoring of GW 170817, the first binary neutron star merger detected by Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo. New observations with the Australian Telescope Compact Array and the Chandra X-ray Telescope were used to constrain its late-time behaviour. The broad-band emission, from radio to X-rays, is well-described by a simple power-law spectrum with index β ∼ 0.585 at all epochs. After an initial shallow rise ∝t0.9, the afterglow displayed a smooth turnover, reaching a peak X-ray luminosity of LX ≈ 5 × 1039 erg s-1 at 160 d, and has now entered a phase of rapid decline, approximately ∝t-2. The latest temporal trend challenges most models of choked jet/cocoon systems, and is instead consistent with the emergence of a relativistic structured jet seen at an angle of ≈22° from its axis. Within such model, the properties of the explosion (such as its blast wave energy EK ≈ 2 × 1050 erg, jet width θc ≈ 4°, and ambient density n ≈ 3 × 10-3 cm-3) fit well within the range of properties of cosmological short gamma-ray bursts.
Volume
489
Issue
2
Start page
1919
Issn Identifier
0035-8711
Ads BibCode
2019MNRAS.489.1919T
Rights
open.access
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