J-PLUS: Spectral evolution of white dwarfs by PDF analysis

Aims. We estimated the spectral evolution of white dwarfs with effective temperature using the Javalambre Photometric Local Universe Survey (J-PLUS) second data release (DR2), which provides 12 photometric optical passbands over 2176 deg(2). Methods. We analyzed 5926 white dwarfs with r <= 19.5 mag in common between a white dwarf catalog defined from Gaia EDR3 and J-PLUS DR2. We performed a Bayesian analysis by comparing the observed J-PLUS photometry with theoretical models of hydrogen- and helium-dominated atmospheres. We estimated the probability distribution functions for effective temperature (T-eff), surface gravity, parallax, and composition; and the probability of having a H-dominated atmosphere (p(H)) for each source. We applied a prior in parallax, using Gaia EDR3 measurements as a reference, and derived a self-consistent prior for the atmospheric composition as a function of T-eff. Results. We described the fraction of white dwarfs with a He-dominated atmosphere (f(He)) with a linear function of the effective temperature at 5000 < T-eff < 30 000 K. We find f(He) = 0.24 +/- 0.01 at T-eff = 10 000 K, a change rate along the cooling sequence of 0.14 +/- 0.02 per 10 kK, and a minimum He-dominated fraction of 0.08 +/- 0.02 at the high-temperature end. We tested the obtained p(H) by comparison with spectroscopic classifications, finding that it is reliable. We estimated the mass distribution for the 351 sources with distance d < 100 pc, mass M > 0.45 M-circle dot, and T-eff > 6000 K. The result for H-dominated white dwarfs agrees with previous studies, with a dominant M = 0.59 M-circle dot peak and the presence of an excess at M similar to 0.8 M-circle dot. This high-mass excess is absent in the He-dominated distribution, which presents a single peak. Conclusions. The J-PLUS optical data provide a reliable statistical classification of white dwarfs into H- and He-dominated atmospheres. We find a 21 +/- 3% increase in the fraction of He-dominated white dwarfs from T-eff = 20 000K to T-eff = 5000 K.