Hot white dwarfs in the Extreme Ultraviolet Explorer survey .1. Properties of a southern hemisphere sample

We present optical spectroscopy of the Balmer line series (H beta through H8) of a sample of 18 hot white dwarfs obtained at the Mount Stromlo and Siding Spring Observatories; the stars are a subset of the white dwarfs detected in the Extreme Ultraviolet Explorer (EUVE) all-sky survey. We analyze the Balmer line profiles conjointly with EUV photometric measurements and provide new effective temperature and surface gravity determinations. We also provide determinations of the neutral hydrogen column density in the interstellar medium toward these lines of Sight. The spectral and photometric properties of most objects in our sample are consistent with emission from pure hydrogen atmospheres. However, we find evidence for the presence of trace absorbers in the photospheres of five of IS objects from the sample - EUVE J0230-479, EUVE J0809-729, EUVE J1546-370, EUVE J2004-560, and EUVE J2324-547. The star EUVE J0230-479 figures among the group of DA white dwarfs with the highest level of metallicity, while EUVE J0809-729 is one of the coolest DA stars (approximate to 30,000 K) to show evidence of trace elements. We also report the discovery of three new massive white dwarf stars-EUVE J1546-367 (M approximate to 1.0 M.), EUVE J1727-360 (M approximate to 1.2 M.), and EUVE J1746-706 (M approximate to 1.4 M.); excluding the two high-mass (M > 1.1 M.) objects from our sample, we obtain an average white dwarf mass of 0.64 M..