Hostname: page-component-cd9895bd7-fscjk Total loading time: 0 Render date: 2024-12-23T19:17:46.723Z Has data issue: false hasContentIssue false
  • English
  • Français

Chemical Stratification in White Dwarf Atmospheres and Envelopes

Published online by Cambridge University Press:  12 April 2016

D. Koester
D. Koester*
Affiliation:
Department of Physics andAstronomy Louisiana State University

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.

The theory of gravitational separation of elements under the combined influence of gravity and electric fields (Schatzman 1958) has been very successful in explaining the general mono-elemental composition observed in most hot white dwarf atmospheres. Today the exceptions to the rule - DO and DAO with mixed compositions (Wesemael et al.1985), DA with traces of helium (Kahn et al. 1984, Petre et al. 1986, Jordan et al.1987, Paerels 1987), DAB (Liebert et al. 1984), and DBA (Shipman et al. 1987) - pose a problem, because they seem to demand a mechanism that counteracts gravitational separation. Such a mechanism that satisfies the observational constraints is very hard to find, and this has led in recent years to the growing conviction that we indeed observe the equilibrium state of diffusion, but in white dwarfs with extremely thin hydrogen layers that remain transparent (at least in the EUV) in many objects (Jordan and Koester 1986, Liebert et al.1987, Vennes et al. 1987, Fontaine et al.1988, Vennes et al.1988).

Type
Research Article
Information
International Astronomical Union Colloquium , Volume 114: White Dwarfs , 1989 , pp. 206 - 219
Copyright
Copyright © Springer-Verlag 1989

References

Arcoragi, J.-P., Fontaine, G. 1980, Astrophys,J. 242, 1208 Google Scholar
Bruhweiler, F.C., Kondo, Y. 1983, Astrophys. J. 269, 657 CrossRefGoogle Scholar
Fontaine, G., Wesemael, F., Vennes, S., Pelletier, C. 1988, paper presented at the 171st. meeting of the American Astronomical Society, Austin, January 1988 Google Scholar
Greenstein, J.L., Peterson, D.M. 1973, Astron. Astrophys. 25, 29 Google Scholar
Hamann, W.R., Kudritzki, R.-P., Mendez, R.H., Pottasch, S.R. 1984, Astron. Astrophys. 139, 459 Google Scholar
Hearn, D.R., Richardson, J.A., Bradt, H.V.D., Clark, G.W., Lewin, W.H.G., Mayer, W.F., Mc-Clintock, J.E., Primini, F.A., Rappaport, S.A. 1976, Astrophys.J. (Letters) 203, L21 Google Scholar
Heise, J., Huizenga, H. 1980, Astron. Astrophys. 84, 280 Google Scholar
Heise, J., Paerels, F.B.S., Bleeker, J.A.M., Brinkman, A.C. 1988, Astrophys. J. in pressGoogle Scholar
Holberg, J.B., Sandel, B.R., Forrester, W.T., Broadfoot, A.L., Shipman, H.L., Barry, J.L. 1980, Astrophys. J. (Letters) 242, L119 Google Scholar
Holberg, J.B. 1987, in IAU Coll.95, The second conference on faint blue stars, ed. Davis Philipp, A.G., Hayes, D.S., Liebert, J. L. Davis Press, Schenectady, p. 285.Google Scholar
Jordan, S., Koester, D. 1986, Astron. Astrophys. Suppl. 65, 367 Google Scholar
Jordan, S., Koester, D., Wulf-Mathies, C., Brunner, H. 1987, Astron. Astrophys. 185, 253 Google Scholar
Kahn, S., Wesemael, F., Liebert, J., Raymond, J., Steiner, J., Shipman, H.L. 1984, Astrophys.J. 278, 255 Google Scholar
Kippenhahn, R., Möllenhoff, C. 1974, Ap. SpaceSci. 31, 117 Google Scholar
Koester, D., Herrero, A. 1988, Astrophys. J. in pressGoogle Scholar
Lampton, M., Margon, B., Paresce, F., Stern, R., Bowyer, S. 1976, Astrophys.J. (Letters) 203, L71 CrossRefGoogle Scholar
Liebert, J., Wesemael, F., Sion, E.M., Wegner, G. 1984, Astrophys.J. 277, 692 Google Scholar
Liebert, J., Fontaine, G., Wesemael, F. 1987, Mem. Soc. Astron. Italiana 58, 17 Google Scholar
Margon, B., Malina, R., Bowyer, S., Stern, R., Paresce, F. 1976a, Astrophys.J. (Letters) 203, L25 Google Scholar
Margon, B., Lampton, M., Bowyer, S., Stern, R., Paresce, F. 1976b, Astrophys.J. (Letters) 210, L79 Google Scholar
Mewe, R., Heise, J., Gronenschild, E.H.B.M., Brinkman, A.C., Shriver, J., den Boggende, A.J.F. 1975a, Nature 256, 711 Google Scholar
Mewe, R., Heise, J., Gronenschild, E.H.B.M., Brinkman, A.C., Shriver, J., den Boggende, A.J.F. 1975b, Astrophys.J. (Letters) 202, L67 Google Scholar
Michaud, G. 1987, in IAU Coll. 95, The second conference on faint blue stars, ed. Davis Philipp, A.G., Hayes, D.S., Liebert, J., L. Davis Press, Schenectady, p. 249 Google Scholar
Muchmore, D. 1982, Astrophys.J. 259, 749 Google Scholar
Muchmore, D. 1984, Astrophys.J. 278, 769 Google Scholar
Paerels, F.B.S., Heise, J. 1988, Astrophys.J. in pressGoogle Scholar
Paerels, F.B.S., Heise, J., Kahn, S.M., Rogers, R.D. 1987, Astrophys.J. 322, 315 Google Scholar
Paerels, F.B.S. 1987, Thesis, University of Utrecht Google Scholar
Paquette, C., Pelletier, C.., Fontaine, G., Michaud, G. 1986, Astrophys.J. Suppl. 61, 197 Google Scholar
Pavlov, G.G., Yakovlev, D.G. 1978, Sov. Astron. 22, 595 Google Scholar
Petre, R., Shipman, H.L., Canizares, C.R. 1986, Astrophys.J. 304, 356 Google Scholar
Pilachowski, C.A., Milkey, R.W. 1984, PASP, 96, 821 Google Scholar
Pilachowski, C.A., Milkey, R.W. 1987, PASP, 99, 836 Google Scholar
Price, C.W., Shipman, H.L. 1985, Astrophys.J. 295, 561 Google Scholar
Schatzman, E. 1958, White Dwarfs, Amsterdam, North Holland Google Scholar
Shipman, H.L. 1988, to appear in IAU Symposium No.131, Planetary Nebulae, D. Reidel, Dordrecht Google Scholar
Shipman, H.L. 1987, in IAU Coll.95, The second conference on faint blue stars, ed. Davis Philipp, A.G., Hayes, D.S., Liebert, J., L. Davis Press, Schenectady, p. 273 Google Scholar
Shipman, H.L., Liebert, J., Green, R.F. 1987, Astrophys.J. 315, 239 CrossRefGoogle Scholar
Tassoul, M., Tassoul, J.-L. 1983, Astrophys.J. 267, 334 Google Scholar
Vauclair, G. 1987, in IAU Coll.95, The second conference on faint blue stars, ed. Davis Philipp, A.G., Hayes, D.S., Liebert, J., L. Davis Press, Schenectady, p. 341 Google Scholar
Vennes, S., Pelletier, C., Fontaine, G., Wesemael, F. 1987, in IAU Coll.95, The second conference on faint blue stars, ed. Davis Philipp, A.G., Hayes, D.S., Liebert, J. L. Davis Press, Schenectady, p. 665 Google Scholar
Vennes, S., Pelletier, C., Fontaine, G., Wesemael, F. 1988, preprint Google Scholar
Wesemael, F., Green, R.F., Liebert, J. 1985, Astrophys.J. Suppl. 58, 379 CrossRefGoogle Scholar