The Compact binary HIgh CAdence Survey (CHiCaS): an overview

Abstract Cataclysmic Variables (CVs) are binaries in which a white dwarf accretes from a low-mass companion star. CVs are the best-suited laboratories to test our understanding of the evolution of compact, interacting binaries as they are numerous, relatively bright, and both stellar components are structurally simple. Nonetheless, while a large fraction ( ≃ 40 - 80 % ) of the present-day Galactic CV population is expected to be old, highly evolved and to host brown dwarf companions, yet very few of these so-called “period bouncers” have been identified so far. The lack of these systems in the observed Galactic CV population possibly suggests that the physical mechanisms driving CV evolution (such as the common envelope phase, the mechanisms of angular momentum loss and/or the response of the companions to the mass loss) are still not completely understood. The Compact binary HIgh CAdence Survey (CHiCaS) is a high cadence photometric survey performing three hours of uninterrupted time series photometry at one minute cadence over 136 square degrees of sky with JAST/T80Cam. CHiCaS aims to unambiguously identify the predicted large population of period-bounce CVs via detection of binary eclipses, thus providing an observational support for the current evolutionary models of all kind of compact binaries, such as black hole binaries, X-ray transients, double degenerates or SN Ia progenitors. Moreover, CHiCaS will deliver high cadence light curves along with full-colour information for about 2.5 million sources, thus identifying several hundred thousand variable stars, including eclipsing and contact binaries, pulsating and flaring stars, which will provide a significant legacy value.