ATLAS: A High-cadence All-sky Survey System

Abstract

Technology has advanced to the point that it is possible to image the entire sky every night and process the data in real time. The sky is hardly static: many interesting phenomena occur, including variable stationary objects such as stars or QSOs, transient stationary objects such as supernovae or M dwarf flares, and moving objects such as asteroids and the stars themselves. Funded by NASA, we have designed and built a sky survey system for the purpose of finding dangerous near-Earth asteroids (NEAs). This system, the "Asteroid Terrestrial-impact Last Alert System" (ATLAS), has been optimized to produce the best survey capability per unit cost, and therefore is an efficient and competitive system for finding potentially hazardous asteroids (PHAs) but also for tracking variables and finding transients. While carrying out its NASA mission, ATLAS now discovers more bright (m < 19) supernovae candidates than any ground based survey, frequently detecting very young explosions due to its 2 day cadence. ATLAS discovered the afterglow of a gamma-ray burst independent of the high energy trigger and has released a variable star catalogue of 5×10 6 sources. This is the first of a series of articles describing ATLAS, devoted to the design and performance of the ATLAS system. Subsequent articles will describe in more detail the software, the survey strategy, ATLAS-derived NEA population statistics, transient detections, and the first data release of variable stars and transient lightcurves.

A Tale of Two Transients: GW 170104 and GRB 170105A

“…Flux errors were calculated as the quadrature sum of the map rms noise, plus a ≈5% fractional error on the measured flux, which accounts for systematics in the absolute flux calibration. Combining all observations, we obtain the source position as R. A.=09:13:13.91, decl.=+61:05:33.6-consistent with the optical position (R.A.=09:13:13.89, decl.=+61:05:33.6; Tonry et al 2017). The source is point-like even at the highest resolution of 0 23 full width at half power.…”

“…ATLAS17aeu was discovered by the Asteroid Terrestrialimpact Last Alert System (ATLAS, Tonry 2011; Tonry et al 2017) as a fast-fading optical transient in the error region of GW170104. To determine the nature of the source and any possible association with GW170104, the GROWTH collaboration undertook the following observations with various telescopes worldwide.…”

“…Searches for a spatially coincident optical counterpart yielded many candidates, which is unsurprising given the dynamic nature of the optical sky (Jinzhong et al 2017;Kasliwal et al 2017b;Lipunov et al 2017aLipunov et al , 2017bSinger et al 2017;Smartt et al 2017;Tonry et al 2017;Tyurina et al 2017). While advances in wide-field optical imaging have overcome the challenge of mapping the coarse localizations of GW triggers, such efforts continue to be plagued by the challenge of false positives i.e., astrophysical events that appear to be both spatially and temporally coincident with the GW trigger but are unrelated (Abbott et al 2016b and references therein).…”

The Early Detection and Follow-up of the Highly Obscured Type II Supernova 2016ija/DLT16am∗

“…Roughly 2 weeks before the discovery of DLT16am, the Type Ic SN 2016iae exploded in NGC1532 (Tonry et al 2016). Pre-SN images of DLT16am were collected during the photometric follow-up campaign of SN2016iae carried out with the Las Cumbres Observatory 1 m telescope network, and these images provided the template images used in our photometric analysis.…”

The Carnegie Supernova Project I

“…In light of current and upcoming surveys such as the All-Sky Automated Survey for Supernovae (ASAS-SN; Shappee et al 2014;Kochanek et al 2017), the Asteroid Terrestrial-impact Last Alert System (ATLAS; Tonry 2011; Tonry et al 2016), the Distance Less Than 40 Mpc survey (DLT40; Tartaglia et al 2017), Pan-STARRS1 (Magnier et al 2013), and the Zwicky Transient Facility (ZTF; Smith et al 2014), progressively more young SE SNe will be discovered within hours of explosion. These early discoveries, coupled with high-cadence spectroscopy at medium or high resolutions, offer the potential to provide new constraints on SE SN progenitors, their pre-SN history, and the reddening of light produced by circumstellar dust.…”