Leung, James K.James K.LeungMurphy, TaraTaraMurphyGHIRLANDA, GiancarloGiancarloGHIRLANDAKaplan, David L.David L.KaplanLenc, EmilEmilLencDobie, DougalDougalDobieBanfield, JulieJulieBanfieldHale, CatherineCatherineHaleHotan, AidanAidanHotanMcConnell, DavidDavidMcConnellMoss, Vanessa A.Vanessa A.MossPritchard, JoshuaJoshuaPritchardRaja, WasimWasimRajaStewart, Adam J.Adam J.StewartWhiting, MatthewMatthewWhiting2022-06-012022-06-0120210035-8711http://hdl.handle.net/20.500.12386/32169We 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<SUP>○</SUP>, 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<SUB>*</SUB> = 3, fractional energy in electrons ϵ<SUB>e</SUB> = 0.3, and fractional energy in magnetic fields ϵ<SUB>B</SUB> = 0.0002.STAMPAen10.1093/mnras/stab3262-s2.0-85115860276https://academic.oup.com/mnras/article/503/2/1847/6129796https://arxiv.org/abs/2102.019482021MNRAS.503.1847LFIS/05 - ASTRONOMIA E ASTROFISICA