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 deg².
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_⊙, and T_eff > 6000 K. The result for H-dominated white dwarfs agrees with previous studies, with a dominant M = 0.59 M_⊙ peak and the presence of an excess at M ∼ 0.8 M_⊙. 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 = 20 000 K to T_eff = 5000 K.

The catalog with the atmospheric parameters and composition of the analyzed white dwarfs is available in electronic form both on the jplus.WhiteDwarf table at the J-PLUS database and at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/658/A79