Probing the extragalactic fast transient sky at minute timescales with DECam. (arXiv:1903.11083v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Andreoni_I/0/1/0/all/0/1">Igor Andreoni</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cooke_J/0/1/0/all/0/1">Jeffrey Cooke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Webb_S/0/1/0/all/0/1">Sara Webb</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rest_A/0/1/0/all/0/1">Armin Rest</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pritchard_T/0/1/0/all/0/1">Tyler A. Pritchard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Caleb_M/0/1/0/all/0/1">Manisha Caleb</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chang_S/0/1/0/all/0/1">Seo-Won Chang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Farah_W/0/1/0/all/0/1">Wael Farah</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lien_A/0/1/0/all/0/1">Amy Lien</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moller_A/0/1/0/all/0/1">Anais Möller</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ravasio_M/0/1/0/all/0/1">Maria Edvige Ravasio</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abbott_T/0/1/0/all/0/1">Timothy M. C. Abbott</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bhandari_S/0/1/0/all/0/1">Shivani Bhandari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cucchiara_A/0/1/0/all/0/1">Antonino Cucchiara</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Flynn_C/0/1/0/all/0/1">Christopher M. Flynn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jankowski_F/0/1/0/all/0/1">Fabian Jankowski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Keane_E/0/1/0/all/0/1">Evan F. Keane</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moriya_T/0/1/0/all/0/1">Takashi J. Moriya</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Onken_C/0/1/0/all/0/1">Christopher Onken</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Parthasarathy_A/0/1/0/all/0/1">Aditya Parthasarathy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Price_D/0/1/0/all/0/1">Daniel C. Price</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Petroff_E/0/1/0/all/0/1">Emily Petroff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ryder_S/0/1/0/all/0/1">Stuart Ryder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wolf_C/0/1/0/all/0/1">Christian Wolf</a>
Searches 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.
Searches 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.
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