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A Turnover in the Radio Light Curve of GW170817

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Authors
Dobie, D.
Kaplan, D.
Murphy, T.
Lenc, E.
Mooley, K.
Lynch, Christene
Corsi, A.
Frail, D.
Kasliwal, M.
Hallinan, G.
Date
2018
Type
Journal Article

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Citation
Dobie, D. and Kaplan, D. and Murphy, T. and Lenc, E. and Mooley, K. and Lynch, C. and Corsi, A. et al. 2018. A Turnover in the Radio Light Curve of GW170817. Astrophysical Journal Letters. 858 (2): Article ID L15.
Source Title
Astrophysical Journal Letters
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Curtin Institute of Radio Astronomy (Physics)
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Copyright © 2018. The American Astronomical Society. All rights reserved.

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Abstract

We present 2-9 GHz radio observations of GW170817 covering the period 125-200 days post-merger, taken with the Australia Telescope Compact Array (ATCA) and the Karl G. Jansky Very Large Array (VLA). Our observations demonstrate that the radio afterglow peaked at 149 ±2 days post-merger and is now declining in flux density. We see no evidence for evolution in the radio-only spectral index, which remains consistent with optically thin synchrotron emission connecting the radio, optical, and X-ray regimes. The peak implies a total energy in the synchrotron-emitting component of a few × 1050erg. The temporal decay rate is most consistent with mildly or non-relativistic material and we do not see evidence for a very energetic off-axis jet, but we cannot distinguish between a lower-energy jet and more isotropic emission.