The solar neighborhood. XIX. Discovery and characterization of 33 new nearby white dwarf systems

We present spectra for 33 previously unclassified white dwarf systems brighter than V 17, primarily in the southern hemisphere. Of these new systems, 26 are DA, 4 are DC, 2 are DZ, and 1 is DQ. We suspect that three of these systems are unresolved double degenerates. We obtained VRI photometry for these 33 objects, as well as for 23 known white dwarf systems without trigonometric parallaxes, also primarily in the southern hemisphere. For the 56 objects, we converted the photometry values to fluxes and fit them to a spectral energy distribution using the spectroscopy to determine which model to use (i.e., pure hydrogen, pure helium, or metal-rich helium), resulting in estimates of T-eff and distance. Eight of the new and 12 of the known systems are estimated to be within the NStars and Catalogue of Nearby Stars horizons of 25 pc, constituting a potential 18% increase in the nearby white dwarf sample. Trigonometric parallax determinations are under way via CTIOPI for these 20 systems. One of the DCs is cool, so it displays absorption in the near-infrared. Using the distance determined via trigonometric parallax, we are able to constrain the model-dependent physical parameters and find that this object is most likely a mixed H/He atmosphere white dwarf similar to other cool white dwarfs identified in recent years with significant absorption in the infrared due to collision-induced absorptions by molecular hydrogen.