Hostname: page-component-848d4c4894-m9kch Total loading time: 0 Render date: 2024-05-18T14:11:24.749Z Has data issue: false hasContentIssue false

An Explanation for the Euv Spectrum of Feige 24

Published online by Cambridge University Press:  12 April 2016

S. Vennes
Affiliation:
Département de Physique, Université de Montréal
P. Chayer
Affiliation:
Département de Physique, Université de Montréal
G. Fontaine
Affiliation:
Département de Physique, Université de Montréal
F. Wesemael
Affiliation:
Département de Physique, Université de Montréal

Extract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Feige 24 is a bright DA white dwarf which has been studied extensively both from ground-based and space-borne observatories. The best determination of its fundamental atmospheric parameters are that of Holberg, Wesemael, and Basile (1986) who have used detailed model atmosphere analyses in conjunction with optical, IUE, and Voyager data. They give log g = 7.23±0.35 and Te(103K) = 55±5. The question of the atmospheric composition is more involved as small traces of heavy elements would not be observable in the optical spectrum of such a hot, hydrogen-dominated atmosphere. If it were isolated, Feige 24 would presumably only show the usual bland optical spectrum of a typical DA white dwarf, i.e. the hydrogen Balmer line series, but the presence of a M dwarf companion complicates its spectrum. On the other hand, Feige 24 belongs to a handful of hot DA white dwarfs sufficiently bright that ultraviolet spectroscopy in the high resolution mode of the IUE has been possible. Following the theoretical expectation of Vauclair, Vauclair, and Greenstein (1979), it was discovered that the photosphere of Feige 24 contains small amounts of C, N, and Si (Dupree and Raymond 1982). Spectral synthesis techniques used by Wesemael, Henry, and Shipman (1984) indicate the following abundances: log(C/H)=−6.4±0.6, log(N/H)=−5.3±1.0, and log(Si/H)=−6.3±0.9. The most plausible explanation to account for these small abundances is the influence of selective radiative forces possibly coupled to a weak wind (Chayer et al. 1987).

Type
Research Article
Copyright
Copyright © Springer-Verlag 1989

References

Bruhweiler, F.C. 1985, Bull. Amer. Asiron. Soc., 17, 559.Google Scholar
Chayer, P., Fontaine, G., Vesemael, F. and Michaud, G. 1987, in IAU Colloquium No. 95, The Second Conference on Faint Blue Stars, Philip, A. G. D., Hayes, D.S. and Liebert, J., eds., L. Davis Press, Schenectady, p. 653. Google Scholar
Chayer, P., Fontaine, G., and Vesemael, F. 1988, these proceedings.Google Scholar
Dupree, A.K., and Raymond, J.C. 1982, Astrophys. J. Letters, 263, L63.Google Scholar
Holberg, J.B., Vesemael, F., and Basile, J. 1986, Astrophys. J., 306, 629.Google Scholar
Holberg, J.B., Sion, E.M., Liebert, J., and Vauclair, G. 1987 Bull. Amer. Astron. Soc., 19, 1041.Google Scholar
Margon, B., Lampton, M., Bowyer, S., Stern, R., and Paresce, J. 1986 Astrophys. J. Letters, 210, L79.Google Scholar
Paerels, F.B.S., Bleeker, J.A.M., Brinkman, A.C., and Heise, J. 1986 Astrophys. J. Letters, 309, L33.Google Scholar
Vauclair, G., Vauclair, S., and Greenstein, J.L. 1979, Astron. Astrophys., 80, 79 Google Scholar
Vennes, S., Pelletier, C., Fontaine, G., and Vesemael, F. 1988, Astrophys. J., in press.Google Scholar
Vennes, S., Fontaine, G., and Vesemael, F. 1988, these proceedings.Google Scholar
Vesemael, F., Henry, R.B.C., and Shipman, H.L., 1984, Astrophys. J., 287, 868.Google Scholar