A database of UV variables from the GALEX surveys

We present the first part of a comprehensive study to search for variability in the UV GALEX archive. GALEX provided photometric measurements for over 200 million objects in FUV and NUV, from sky surveys with different depth and coverage. In this work we extract 410,408 unique sources showing variability (ΔNUV⩾0.6mag , ΔFUV⩾0.4mag) in both NUV and FUV from a total of 2,106,816 measurements. We restrict our analysis to 7264 sources that have at least 30 measurements, sampled with serendipitous time coverage. This first sample selection includes both extragalactic sources and Milky Way stellar objects, displaying both periodic and non-periodic variability, of various types including RR Lyrae, flare stars, transients, and eclipsing binaries. Amplitudes of magnitude variations are found from our minimum selection threshold up to several magnitudes. We describe the selection criteria and procedures, we characterize the main classes of variables within the sample, and present the layout of the resulting catalog which will be also made available as on-line resource. Beyond our immediate goals of discovering and characterizing UV-selected variables, this work provides synergy with existing and planned surveys at other wavelengths (e.g. SDSS, PanSTARRS, LSST, GAIA).