Deep Canada-France-Hawaii Telescope photometric survey of the entire M33 galaxy - I. Catalogue of 36 000 variable point sources

We have conducted a variability survey of the Local Group galaxy M33, using g', r', and i' observations from 27 nights spanning 17 months, made with the MegaPrime/MegaCam instrument on the 3.6-m Canada-France-Hawaii Telescope (CFHT). We identify more than 36 000 variable sources with g', r', i' less than or similar to 24, out of approximately two million point sources in a 1-deg(2) field of view. This increases the number of known variables in this galaxy by more than a factor of 20. In this paper, we provide a brief description of the data and a general overview of the variable star population which includes more than 1300 candidate variable blue and red supergiant stars, more than 2000 Cepheids, and more than 19 000 long-period variable asymptotic giant branch and red giant branch stars.