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

ABSTRACT We present a search for radio afterglows from long gamma-ray bursts using the Australian Square Kilometre Array Pathfinder (ASKAP). Our used Rapid ASKAP Continuum Survey, covering entire celestial sphere south of declination +41○, and three epochs Variables Slow Transients Pilot Survey (Phase 1), ∼5000 square degrees per epoch. The observations we these surveys spanned nine-month period 2019 April 21 to 2020 January 11. cross-matched sources found in with 779 well-localized (to ≤15 arcsec) occurring after 2004 determined whether associations were more likely afterglow- or host-related through analysis optical images. In our search, detected one afterglow candidate associated GRB 171205A, local low-luminosity burst supernova counterpart SN 2017iuk, an observation 511 d post-burst. confirmed this detection further Australia Telescope Compact at 859 884 Combining data archival early-time observations, showed evolution spectral energy distribution alone could reveal clear signatures wind-like circumburst medium burst. Finally, derived semi-analytical estimates microphysical shock parameters burst: electron power-law index p = 2.84, normalized wind-density parameter A* 3, fractional electrons ϵe 0.3, magnetic fields ϵB 0.0002.