Hot degenerates in the MCT survey. I. MCT 130-1937, a new, color-selected PG 1159 object

Abstract

We report the discovery, in the course of a survey for high-latitude, ultraviolet-excess objects in the southern hemisphere, of a new white dwarf star belonging to the PG 1159 spectroscopic class. A variety of spectroscopic observations show this object to be similar to the prototype PG 1159-035 in exhibiting He u, C IV, and O VI features in its optical spectrum, as well as a rich absorption spectrum in the ultraviolet. In addition, the slope of its energy distribution appears as steep as that of PG 1159-035 and is consistent with the Rayleigh-Jeans tail of a very hot ('I;, 100,000 K) star. White-light, high-speed photometry reveals that this object does not exhibit periodic variations in the range 10-2000 s with semiamplitudes larger than 0.002 mag. The importance of such objects for current models of the spectral evolution of white dwarfs is emphasized.