Masses and Radii of White Dwarf Stars as Determined from the Model Atmosphere Approach.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Masses and Radii of White Dwarf Stars as Determined from the Model Atmosphere Approach. Terashita, Yoichi ; Matsushima, Satoshi Abstract An attempt has been made to determine masses and radii of DA type white dwarf stars from observed UB V colors and luminosities. The model atmospheres have been computed including the blanketing effect due to Lyman and Balmer series lines. In computing the line profiles, we have used the Stark broadening formula recently given by Griem (Astrophys. J. 147, 1092, 1967). The color diagram appears systematically different from that previously obtained from the models without blanketing (Terashita and Matsushima, Astrophys. J. Suppi. 13, 461,1966). Effective temperatures thus determined for individual stars are in general about 25% higher than those which we would obtain from interpolations between the blackbody curve and that of the main sequence stars. Since these temperatures give radii smaller than those based on the above- mentioned interpolarion method, they seem to be more preferable in interpreting the recent observations of gravitational redshift by Greenstein and Trimble (to be published). A division of white dwarfs into two sequences with different radii is confirmed for a certain temperature region, but in other regions the separation is not clear. Among the DA stars with known parallaxes, we have been able to determine Te and log g of 20 stars, and thus their masses and radii. All the high-temperature stars seem to satisfy the theoretical mass- radius relations predicted by Hamada and Salpeter (Astrophys. J. 134, 683,1961). For stars with lower temperatures some deviations from the theoretical relations are seen, and they appear to be related to the existence of the two equi-radius sequences. We have obtained M/Mo=0.38 for 40 Eri B which gives a satisfactory agreement with the observed value of 0.43. This research was supported in part by the Xational Science Foundation under grant GP-4742. Publication: The Astronomical Journal Pub Date: 1967 DOI: 10.1086/110467 Bibcode: 1967AJ.....72Q.832T full text sources ADS |