Abstract
High signal-to-noise optical spectrophotometry of a sample of field subluminous B stars drawn largely from the Palomar Green UV excess survey is analyzed with a new grid of model atmospheres and synthetic spectra. The effective temperatures, surface gravities, and photospheric helium abundances are determined simultaneously from an analysis of hydrogen and helium absorption line profiles. The derived temperatures and gravities place the helium-deficient sdB stars in the H—R diagram along and just above theoretical sequences of the zero-age extended horizontal branch, lending strong support to the hypothesis that these stars are composed of helium-burning cores of ∼0.5M ⊙ overlain by very thin (\(\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\thicksim}$}}{<}\), 0.02M ⊙) layers of hydrogen. Various scenarios for their past evolutionary history are examined in the context of their probable future evolution into low-mass white dwarfs.
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References
Allen, C.W. 1973, Astrophysical Quantities, (London: Athlone).
Armandroff, T.E. 1988, A. J., 96, 588.
Baschek, B. and Norris, J. 1975, Ap. J., 199, 694.
Bergeron, P., Fontaine, G., Lacombe, P., and Wesemael, F. 1984, A. J., 89, 374
Bergeron, P., Fontaine, G., Lacombe, P., and Wesemael, F. 1984, A. J., 89, 374
Bergeron, P., Fontaine, G., Lacombe, P., and Wesemael, F. 1984, A. J., 89, 374
Bergeron, P., Saffer, R.A., and Liebert, J. 1991b, these proceedings.
Caloi, V. 1972, Astr. Ap., 20, 357.
Caloi, V. 1989, Astr. Ap., 221, 27.
Daou, D., Wesemael, F., Bergeron, P., Fontaine, G., and Holberg, J.B. 1990, Ap. J., 364, 242.
Downes, R.A. 1986, Ap. J. Suppl., 61, 569.
Fontaine, G., Wesemael, F., Lamontagne, R., Bergeron, P., and Green, R.F. 1987, I.A.U. Colloquium No. 95, The Second Conference on Faint Blue Stars, eds. Philip et al. (Schenectady: Davis), p. 615.
Green, R.F., Schmidt, M., and Liebert, J. 1986. Ap. J. Suppl., 61, 305.
Greenstein, J.L. 1971, IAU Symposium No. 42, White Dwarfs, ed. W.J. Luyten (Dordrecht: Reidel), p. 46.
Greenstein, J.L. and Sargent, A.I. 1974, Ap. J. Suppl., 28, 157.
Groth, H.G., Kudritzki, R.P., and Heber, U. 1985, Astr. Ap., 152, 107.
Heber, U. 1986, Astr. Ap., 155, 33.
Heber, U., Hunger, K., Jonas, G., Simon, K.P., 1984, Astr. Ap., 130, 119.
Heber, U., Kudritzki, R.P., Caloi, V., Castellani, V., Danziger, J., and Gilmozzi, R. 1986, Astr. Ap., 162, 171.
Hummer, D. G. and Mihalas, D. 1988, Ap. J., 331, 794.
Hunger, K., Gruschinske, J., Kudritzki, R.P., and Simon, K.P. 1981, Astr. Ap., 95, 244.
Iben, I. 1990, Ap. J., 353, 215.
Iben, I. and Tutukov, A.V. 1986a, Ap. J., 311, 742.
Iben, I. and Tutukov, A.V. 1986b, Ap. J., 311, 753.
Kudritzki, R. D. and Hummer, D. 1990, Ann. Rev. Astr. Ap., 20, 303.
Mendez, R.H., Miguel, C.H., Heber, U., and Kudritzki, R.P. 1986, I.A.U. Colloquium No. 87, Hydrogen Deficient Stars and Related Objects, eds. Hunger et al. (Dordrecht: Reidel), p. 323.
Michaud, G., Bergeron, P., Wesemael, F., and Fontaine, G. 1985, Ap. J., 299, 741.
Michaud, G., Bergeron, P., Heber, U., and Wesemael, F. 1989, Ap. J., 338, 417.
Moehler, S., Richtler, T., de Boer, K.S., Dettmar, R.J., and Heber, U. 1990, Astr. Ap. Suppl., 86, 53.
Moehler, S., Heber, U., and de Boer, K.S. 1990, Astr. Ap., in press.
Paczyński, B. 1971, Acta Astr., 21, 1.
Saffer, R. A., Bergeron, P., Liebert, J., and Koester, D. 1991, in preparation.
Saffer, R.A. and Liebert, J. 1991, in preparation.
Schönberner, D. and Drilling, J.S. 1984, Ap. J., 278, 702.
Sweigart, A.B. 1987, Ap. J. Suppl., 65, 95.
Wesemael, F., Auer, L.H., Van Horn, H.M., and Savedoff, M.P. 1980, Ap. J. Suppl., 43, 159.
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Saffer, R.A., Bergeron, P., Liebert, J., Koester, D. (1991). Atmospheric Parameters of Subluminous B Stars. In: Vauclair, G., Sion, E. (eds) White Dwarfs. NATO ASI Series, vol 336. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-3230-5_6
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DOI: https://doi.org/10.1007/978-94-011-3230-5_6
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