White dwarfs

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The aim of this thesis is to use model-atmosphere techniques and intermediate-band photoelectric scans to determine the properties of white dwarfs. Model atmospheres have been calculated with [...] for solar composition and [...] for helium-rich (Y=1) models. Photoelectric scans of some 37 white dwarfs are the observational basis of the thesis. The essential results for the program stars are that the DA stars have a mean radius of .013 [...]. With one or two exceptions, the program stars are on the upper sequence of the white dwarfs. The median mass is 0.58 [...]. One of the DA,F stars in the program L 870-2, has a radius of .04 [...]. The DA stars cover a wide range of effective temperature; the DB stars, with the exception of HZ 29, have 12,000°[...]18,000°K. The DA stars contain very little helium ([...]0.8% by number); and the DB stars contain very little metals. It is possible to interpret the spectrum of the one DC star in the program (L 1363-3) as a cooled-off DB star, since the helium lines fade out at [...]. The spectrum of Sirius B is analyzed; the hydrogen line profiles, combined with the mass of 1.02[...] (van den Bos 1960) and the visual magnitude of 8.29 (Lindenblad 1970) yield an effective temperature of 32,000°K and a surface gravity of 8.65, corresponding to a radius of 0.0078 [...]. These values are consistent with the measured gravitational redshift of +88 km/sec. Using the program stars, I then define a U-V versus [...] relation for DA stars and for the DB and DC stars. Using this relation, and the [...] as measured by Graham (1969), I compute masses and radii for a much larger sample of white dwarfs than the program stars those with known distances. The median radius of these stars, which include quite a few on the lower sequence is 0.0095 [...]. Using these data, I find that the atmospherically derived masses of white dwarfs are in