The first data release of J-VAR: Multi-filter light curves for 1.3 million point-like sources

Context. The Javalambre VARiability survey (J-VAR) is a multi-filter photometric survey conducted at the Observatorio Astrofísico de Javalambre, covering selected regions of the northern sky, and providing time-domain information for the Javalambre Photometric Local Universe Survey (J-PLUS) fields. J-VAR primarily focuses on small bodies of the Solar System, variable stars, and optical transients. Aims. We aim to present and describe the data set of light curves contained in this first data release of J-VAR. Methods. J-VAR observations were conducted in seven filters observed quasi-simultaneously, three SDSS broad-bands (g, r, and i), and four narrow bands of the J-PLUS filter system (J0395, J0515, J0660, and J0861). As J-VAR is executed primarily in multi-epoch mode, with multiple visits to a given field spread over a period of a year, the data were collected under varying atmospheric and sky brightness conditions. We accounted for these variations by employing an ensemble differential-photometry technique to correct the light curves, which were subsequently calibrated using already available J-PLUS photometry. Additionally, we used a classification scheme based on Bayesian neural networks to select a high-confidence sample of point-like sources (stars and quasi-stellar objects (QSOs)). Results. J-VAR DR1 consists of 101 fields, covering about 200 square degrees on the sky and containing the light curves of more than 1.3 million point-like sources in the seven filters. The light curves span an effective magnitude range from 13 to 19, with a photometric root mean square (RMS) precision of 2% down to a magnitude of ∼16 and 5% to a magnitude of ∼18 in the broad-band filters. Furthermore, we calculated and provide a number of different variability indices for the light curves included in this data release.