Empirical masses and radii, computed adopting the radial velocity measured from the Hα+Hβ lines together (left panel) and Hα line only (right panel), are overplotted onto theoretical relations. The color-scheme maps the measured T_eff, while the inclined error bars account for the mass/radius correlation. Symbols represent the SPY sample (squares) and new UVES data (circles); up-/down-pointing triangles are used in the right panel for the DAH white dwarf, when it is analyzed with convective (Tremblay et al. 2011) or radiative models (Tremblay et al. 2015a), respectively. The theoretical curves account for different core-compositions (He, CO, and ONe; see Fig. 9 for comparison and Althaus et al. 2013; Camisassa et al. 2016, 2019, for more details). The mass-radius relation for Fe-core white dwarfs (Panei et al. 2000) is represented by dashed lines. (a) v_WD measured from the Hα+Hβ lines. (b) v_WD measured from the Hα line.

Fig. 9.

Distribution of gravitational redshifts as a function of log T_eff. The theoretical curves are plotted as solid lines, which are labeled based on the corresponding mass and core compositions (He-, CO-, and ONe-cores Althaus et al. 2013; Camisassa et al. 2016, 2019). For reference, we also plot the models for two ultra-massive CO-core white dwarfs of 1.23 and 1.29 M_⊙ (Camisassa et al. 2022) and the relativistic models for the 1.3 M_⊙ ONe- and the 1.29 M_⊙ CO-core white dwarfs (dashed curves; Althaus et al. 2022, 2023). The observed stars are color coded accordingly to their measured masses; the adopted symbols are the same as in Fig. 8. The four labeled stars are discussed in the text.