Discovery of two new pulsating DA (ZZ Ceti) white dwarfs

We report the detection of multiperiodic luminosity variations in the light curves of the two DA white dwarfs GD 244 and KUV 02464+3239. We selected t hese objects as candidate ZZ Ceti stars on the basis of our analysis of the ir optical spectra, which revealed that their atmospheric parameters place them inside the empirical instability strip in the log g-T-eff plane. We fi nd that GD 244 is an intermediate-amplitude pulsator with at least four exc ited modes with periods in the range 203-307 s, which is consistent with it s position in the middle of the ZZ Ceti instability strip at T-eff = 11,680 K and log g = 8.08. We compare the properties of GD 244 with those of GD 6 6, a previously known ZZ Ceti star that appears to be a photometric clone o f the former. We also find that KUV 02464+3239 is a large-amplitude, long-p eriod variable, which is again consistent with its position at T-eff = 11,2 90 K and log g = 8.08 in the log g-T-eff diagram, near the red edge of the empirical instability strip. The light curve of KUV 02464+3239 is dominated by a quasi-period of similar to 832 s and resembles that of its photometri c twin GD 154. Our findings bring to 31 the number of known gravity-mode ZZ Ceti pulsators.