Atmospheric parameters and mass distribution of DA-white dwarfs

1983 ◽  
Vol 96 (1) ◽  
pp. 1-23 ◽  
Author(s):  
O. H. Guseinov ◽  
H. I. Novruzova ◽  
Y. S. Rustamov
1997 ◽  
Vol 488 (1) ◽  
pp. 375-396 ◽  
Author(s):  
David S. Finley ◽  
Detlev Koester ◽  
Gibor Basri

1989 ◽  
Vol 114 ◽  
pp. 244-248
Author(s):  
D. Daou ◽  
F. Wesemael ◽  
P. Bergeron ◽  
G. Fontaine ◽  
J. B. Holberg

The pulsating ZZ Ceti stars cover a narrow range of effective temperatures along the cooling sequence of DA white dwarfs (see, eg., Winget and Fontaine 1982). Fast-photometric searches for pulsating stars in that class have provided strong evidence that the ZZ Ceti phase is an evolutionary phase through which all cooling DA stars will eventually go through (Fontaine et al. 1982). Recent investigations, based on optical or ultraviolet photometry and spectrophotometry, have set the boundaries of the instability strip at temperatures near 10,000-11,000 K and 12,000-13,000 K, respectively (McGraw 1979; Greenstein 1982; Weidemann and Koester 1984; Fontaine et al. 1985; Wesemael, Lamontagne, and Fontaine 1986; Lamontagne, Wesemael, and Fontaine 1987, 1988).


1971 ◽  
Vol 42 ◽  
pp. 125-129
Author(s):  
I. Bues

The determination of atmospheric parameters for non-DA white dwarfs is investigated with the computed helium-rich model atmospheres by Bues (1970). Only poor predictions are possible from UBV colors alone for DB and DC stars. From uvby colors a determination of effective temperature is possible within 1000 K. Profiles of lines in different parts of the spectrum are necessary for better results.A deficiency of metal abundances for the cooler non-DA stars is obtained.


1999 ◽  
Vol 517 (1) ◽  
pp. 399-415 ◽  
Author(s):  
R. Napiwotzki ◽  
Paul J. Green ◽  
Rex A. Saffer

1984 ◽  
Vol 100 (1-2) ◽  
pp. 471-473 ◽  
Author(s):  
D. Koester

1989 ◽  
Vol 114 ◽  
pp. 1-14 ◽  
Author(s):  
Volker Weidemann ◽  
Jie W. Yuan

Ever since Graham’s Strömgren photometry (1972) demonstrated the existence of a single well defined cooling sequence of DA white dwarfs the question of the mass dispersion (or the width of the number-mass distribution) has been in the foreground of my studies (Weidemann, 1970, 1977).Indeed it turned out that the shape of the white dwarf mass distribution provides strong constraints on the theory of stellar evolution with mass loss, a fact which will be demonstrated again in the following lecture. It therefore seems worthwhile to dwell in some detail on the methods of its determination. For the benefit of the non-specialists I shall first present some of the historical results and then continue to discuss the present situation.


1990 ◽  
Vol 122 ◽  
pp. 392-393
Author(s):  
M. Politano ◽  
R.F. Webbink

A zero-age cataclysmic variable (ZACV) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACVs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years. These results differ from previous work (Politano and Webbink 1988) in that an improved criterion for stability against rapid mass transfer by the secondary to the white dwarf has been used. A brief outline of the method and key assumptions made in this calculation is given in Politano and Webbink (1988).The white dwarf mass distribution of ZACVs (shown in Figure 1) contains two components: systems with helium white dwarfs and systems with C-0 white dwarfs. Systems with helium white dwarfs comprise slightly greater than 50% of all ZACVs. The helium white dwarfs have masses which range from 0.27 to 0.46 solar mass. The C-0 white dwarfs have masses which range from 0.54 solar mass up to the Chandrasekhar mass. (Note: systems with O-Ne-Mg white dwarfs are not distinguished from systems with C-0 white dwarfs in this calculation. Presumably, these O-Ne-Mg systems comprise the upper end of the white dwarf mass distribution.)


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