White Dwarf Atmospheres.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS White Dwarf Atmospheres. Terashita, Yoichi ; Matsushima, Satoshi Abstract A network of 20 nongray model atmospheres and hydrogen line profiles have been computed for white dwarfs with effective temperatures ranging from 80000 to 25 0000K and logarithmic surface gravities between 6 and 9. Assuming a standard chemical composition and taking H-, H, He, and He+ as sources of continuous opacity, the calculations are made on the basis of the Avrett- Krook iteration procedure including the pre-lonization effect. It has been found that the effect of Balmer lines is more important than the pre-lonization except for regions very close to the Balmer discontinuity. UB V colors calculated from the emergent flux place each of the above models on a (U-B, B-V) diagram, forming an interpolation scheme to determine a set of Te and g values for a star from the observed colors. Thus, Te and log g values are determined for about 90 DA-type white dwarfs for which the photometric data and H7 equivalent widths are given by Eggen and Greenstein (Astrophys. J. 141, 83, 1965). At the same time, "isoequivalent-width" curves are constructed on a Te-log g domain, on which theoretical values of W (H7) are estimated for the same group of stars. A comparison of the observed equivalent widths with the above predicted values has shown a good agreement indicating the consistency in the computations of colors and line intensities. Further comparisons of the detailed profiles of H7 lines with those ob- served by Greenstein [Stellar Atmospheres (University of Chicago Press, Chicago, 1960), Chap. 19] for 20 of these stars have shown excellent fit except for a few DAwk type stars. The established values of both the reciprocal temperature and the surface gravity are smaller than those previously estimated by Weidemaun (Z. Astrophys. 57, 87, 1963) for practically all the stars. This work has been supported in part by a grant GP-4742 from the National Science Foundation. Publication: The Astronomical Journal Pub Date: 1965 DOI: 10.1086/109834 Bibcode: 1965AJ.....70R.694T full text sources ADS |