We present an improved spectroscopic and photometric analysis of hydrogen-line DA white dwarfs from the Sloan Digital Sky Survey Data Release 4 (SDSS DR4) based on model atmospheres that include improved Stark broadening profiles with non-ideal gas effects. We also perform a careful visual inspection of all spectroscopic fits with high signal-to-noise ratios (S/Ns>12) and present improved atmospheric parameters (T_eff_ and logg) for each white dwarf. Through a comparison of spectroscopic and photometric temperatures, we report the discovery of 35 DA+DB/DC double degenerate candidates and two helium-rich DA stars. We also determine that a cutoff at S/N=15 optimizes the size and quality of the sample for computing the mean mass of DA white dwarfs, for which we report a value of 0.613M_{sun}_. We compare our results to previous analyses of the SDSS DR4 and find a good agreement if we account for the shift produced by the improved Stark profiles. Finally, the properties of DA white dwarfs in the SDSS are weighed against those of the Villanova White Dwarf Catalog sample of Gianninas et al. (2009JPhCS.172a2021G).

Cone search capability for table J/ApJ/730/128/table1 (SDSS DR4 sample of DA white dwarfs with S/N>12)

Cone search capability for table J/ApJ/730/128/table3 (DA+DB/DC binary candidates)

Cone search capability for table J/ApJ/730/128/table5 (SDSS DR4 sample of DAO white dwarfs with S/N>12)