A search for radio afterglows from gamma-ray bursts with the Australian Square Kilometre Array Pathfinder

Journal
Date Issued
2021
Author(s)
Leung, James K.
•
Murphy, Tara
•
•
Kaplan, David L.
•
Lenc, Emil
•
Dobie, Dougal
•
Banfield, Julie
•
Hale, Catherine
•
Hotan, Aidan
•
McConnell, David
•
Moss, Vanessa A.
•
Pritchard, Joshua
•
Raja, Wasim
•
Stewart, Adam J.
•
Whiting, Matthew
DOI
Abstract
We present a search for radio afterglows from long gamma-ray bursts using the Australian Square Kilometre Array Pathfinder (ASKAP). Our search used the Rapid ASKAP Continuum Survey, covering the entire celestial sphere south of declination +41○, and three epochs of the Variables and Slow Transients Pilot Survey (Phase 1), covering ~5000 square degrees per epoch. The observations we used from these surveys spanned a nine-month period from 2019 April 21 to 2020 January 11. We cross-matched radio sources found in these surveys with 779 well-localized (to ≤15 arcsec) long gamma-ray bursts occurring after 2004 and determined whether the associations were more likely afterglow- or host-related through the analysis of optical images. In our search, we detected one radio afterglow candidate associated with GRB 171205A, a local low-luminosity gamma-ray burst with a supernova counterpart SN 2017iuk, in an ASKAP observation 511 d post-burst. We confirmed this detection with further observations of the radio afterglow using the Australia Telescope Compact Array at 859 and 884 d post-burst. Combining this data with archival data from early-time radio observations, we showed the evolution of the radio spectral energy distribution alone could reveal clear signatures of a wind-like circumburst medium for the burst. Finally, we derived semi-analytical estimates for the microphysical shock parameters of the burst: electron power-law index p = 2.84, normalized wind-density parameter A* = 3, fractional energy in electrons ϵe = 0.3, and fractional energy in magnetic fields ϵB = 0.0002.
Volume
503
Issue
2
Start page
1847
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2021MNRAS.503.1847L
Rights
open.access
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