Andreoni, IgorCooke, JeffreyWebb, SaraRest, ArminPritchard, Tyler A.Caleb, ManishaChang, Seo-WonFarah, WaelLien, AmyMöller, AnaisRavasio, Maria EdvigeAbbott, Timothy M. C.Bhandari, ShivaniCucchiara, AntoninoM. Flynn, ChristopherJankowski, FabianKeane, Evan F.Moriya, Takashi J.Onken, ChristopherParthasarathy, AdityaPrice, Daniel C.Petroff, EmilyRyder, StuartWolf, Christian2019-04-262019-04-262019-03-26Igor Andreoni, et.al, Probing the extragalactic fast transient sky at minute timescales with DECam, Astrophysics, High Energy Astrophysical Phenomena, 2019, https://arxiv.org/abs/1903.11083http://hdl.handle.net/11603/13518Searches for optical transients are usually performed with a cadence of days to weeks, optimised for supernova discovery. The optical fast transient sky is still largely unexplored, with only a few surveys to date having placed meaningful constraints on the detection of extragalactic transients evolving at sub-hour timescales. Here, we present the results of deep searches for dim, minute-timescale extragalactic fast transients using the Dark Energy Camera, a core facility of our all-wavelength and all-messenger Deeper, Wider, Faster programme. We used continuous 20 s exposures to systematically probe timescales down to 1.17 minutes at magnitude limits g > 23 (AB), detecting hundreds of transient and variable sources. Nine candidates passed our strict criteria on duration and non-stellarity, 5 of which could later be classified as flare stars, but 4 of which have more unsure classification. Searches for fast radio burst and gamma-ray counterparts during simultaneous multi-facility observations yielded no counterparts to those 4 optical transients. Also, no long-term variability was detected with pre-imaging and follow-up observations using the SkyMapper optical telescope. We place (conservative) upper limits and (optimistic) measurements of minute-timescale fast optical transient rates for a range of depths and timescales. Finally, we demonstrate that optical g-band light curve behaviour alone cannot discriminate between confirmed extragalactic fast transients such as prompt GRB flashes and Galactic stellar flares.20 pagesen-USThis item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.supernovaegeneral - starsflare - gamma-ray burstgeneral - radio continuumtransientsText