The High Cadence Transient Survey (Hits). I. Survey Design and Supernova Shock Breakout Constraints

Abstract

We present the first results of the High Cadence Transient Survey (HiTS), a survey for which the objective is to detect and follow-up optical transients with characteristic timescales from hours to days, especially the earliest hours of supernova (SN) explosions. HiTS uses the Dark Energy Camera and a custom pipeline for image subtraction, candidate filtering and candidate visualization, which runs in real-time to be able to react rapidly to the new transients. We discuss the survey design, the technical challenges associated with the real-time analysis of these large volumes of data and our first results. In our 2013, 2014, and 2015 campaigns, we detected more than 120 young SN candidates, but we did not find a clear signature from the short-lived SN shock breakouts (SBOs) originating after the core collapse of red supergiant stars, which was the initial science aim of this survey. Using the empirical distribution of limiting magnitudes from our observational campaigns, we measured the expected recovery fraction of randomly injected SN light curves, which included SBO optical peaks produced with models from Tominaga et al. (2011) andSari (2010). From this analysis, we cannot rule out the models from Tominaga et al. (2011) under any reasonable distributions of progenitor masses, but we can marginally rule out the brighter and longer-lived SBO models from Nakar & Sari (2010) under our best-guess distribution of progenitor masses. Finally, we highlight the implications of this work for future massive data sets produced by astronomical observatories,such as LSST.

Fast Algorithms for Slow Moving Asteroids: Constraints on the Distribution of Kuiper Belt Objects

“…We tested our software using the first three nights (February 17-19, 2015) of the 2015 campaign of the High Cadence Transient Survey (HiTS) (Förster et al 2016). The 2015 HiTS campaign involved repeatedly visiting 50 3-square-degree fields in the DECam g-band filter.…”

Mapping the Tidal Destruction of the Hercules Dwarf: A Wide-field DECam Imaging Search for RR Lyrae Stars

“…To assess the possibility of our new RR Lyrae stars being Milky Way halo stars instead of tidal debris from Hercules, we look at new data on the RR Lyrae star density as a function of Galactocentric distance from the High Cadence Transient Survey (HiTS; Förster et al 2016;Medina et al 2017, in preparation), which indicate a RR Lyrae star halo density of ∼ 10 −4 kpc -3 at the distance of Hercules, where their completeness is ∼ 85%. To estimate the volume probed by our RR Lyrae star search, we first find the area covered by DECam's field of view to be 16.7 kpc 2 .…”

Asteroids’ Size Distribution and Colors from HITS

“…For this, it combined high cadence with a high limiting magnitude and a wide field of view. These characteristics offer the opportunity to do science in various topics other than supernovae (Förster et al 2016 such as RR Lyrae (Medina et al 2017(Medina et al , 2018, SS minor bodies (Peña et al 2018 and this work) and automatic classification of variable sources (Martínez-Palomera et al 2018).…”