Abstract
Like many path-breaking events, the discovery of white dwarf pulsations happened serendipitously. In the mid-1960s, Arlo Landolt, an observational astronomer at Louisiana State University (LSU), was conducting photometric observations of some faint variable stars at the Kitt Peak National Observatory in the mountains near Tucson, Arizona. To help in counteracting variations in atmospheric transmission, Landolt performed his observations by first taking a photometric exposure on a target star and then switching to take a similar exposure on a nearby, faint star that was not variable. Alternating between the two stars every few minutes, Landolt built up a time series of observations that followed the variations in the target star’s luminosity. In processing his data later, he planned to use the recorded observations of the non-variables to establish a steady baseline against which to measure the variability of his target stars.
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Notes
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Landolt, A. U. 1968, Astrophys. J., 153, 151, “A New Short-Period Blue Variable.”
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Sauvenier-Goffin, E. 1949, Ann. d’Astrophys., 12, 39, “La Stabilité Dynamique des Naines Blanches.”
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Landolt (1968), op. cit.
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Robinson, E. L., in Van Horn and Weidemann (1979), p. 343, “The Observational Properties of the ZZ Ceti Stars.”
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Winget, D. E., and Van Horn, H. M. 1982, Sky & Tel., 64, 216, “ZZ Ceti Stars: Variable White Dwarfs.”
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Similar conclusions about the effects on white dwarf pulsations of stratified surface layers were reached by Dziembowski, W., and Koester, D. 1981, Astron. & Astrophys., 97, 16, “Excitation of Gravity Modes in White Dwarfs with Chemically Stratified Envelopes,” and by Dolez, N., and Vauclair, G. 1981, Astron. & Astrophys., 102, 375, “Gravity Modes in ZZ Ceti Stars. I. Quasi-Adiabatic Analysis of Overstability.”
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Kepler, S. O. 2007, Comm. In Asteroseismology, 150, 221, “Observational White Dwarf Sesimology.”
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Winget, D. E., et al. 1982, Astrophys. J., 252, L65, “Hydrogen-Driving and the Blue Edge of Compositionally Stratified ZZ Ceti Star Models.”
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Winget, D. E., et al. 1982, Astrophys. J., 262, L11, “Photometric Observations of GD 358: DB White Dwarfs Do Pulsate.”
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Kepler (2007), op. cit.
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Winget et al. (1982), op. cit.
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Beauchamp. A., et al. 1999, Astrophys. J., 516, 887, “Spectroscopic Studies of DB White Dwarfs: The Instability Strip of the Pulsating DB (V777 Her) Stars.”
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Ibid.
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Green (1977).
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McGraw, J. T., et al., in Van Horn and Weidemann (1979), p. 377, “PG 1159-035: A New, Hot, Non-DA Pulsating Degenerate.”
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Wesemael, F., Green, R. F., and Liebert, J. W. 1985, Astrophys. J. Suppl., 58, 379, “Spectrophotometric and Model-Atmosphere Analyses of the Hot DO and DAO White Dwarfs from the Palomar-Green Survey.”
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Barstow, M., et al. 1986, Astrophys. J., 306, L25, “The Detection of Photospheric X-Ray Pulsations from PG1159-035 with EXOSAT.”
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Brickhill, A. J. 1983, Mon. Not. Roy. Astron. Soc., 204, 537, “The Pulsations of ZZ Ceti Stars.”
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Dolez, N., and Vauclair, G. 1981, Astron. & Astrophys., 102, 375, “Gravity Modes in ZZ Ceti Stars. I. Quasi-Adiabatic Analysis of Overstability.”
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Wu (1998); see also Goldreich, P., and Wu, Y. 1999a, Astrophys. J., 511, 904, “Gravity Modes in ZZ Ceti Stars. I. Quasi-Adiabatic Analysis of Overstability;” Wu, Y., and Goldreich, P. 1999, Astrophys. J., 519, 783, “Gravity Modes in ZZ Ceti Stars. II. Eigenvalues and Eigenfunctions;” and Goldreich, P., and Wu, Y. 1999b, Astrophys. J., 523, 805, “Gravity Modes in ZZ Ceti Stars. III. Effects of Turbulent Dissipation.”
References
Green, R. F. 1977, Ph.D. thesis, Caltech, “A Complete Sample of White Dwarfs, Hot Subdwarfs, and Quasars.”
Van Horn, H. M., and Weidemann, V., eds. 1979, White Dwarfs and Variable Degenerate Stars (University of Rochester: Rochester, New Yprk).
Winget, D. E. 1981, Ph.D. thesis, University of Rochester, “Gravity Mode Instabilities in DA White Dwarfs.”
Wu, Yanqin 1998, Ph.D. thesis, California Institute of Technology, “Excitation and Saturation of White Dwarf Pulsations.”
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Van Horn, H.M. (2015). Music of the Spheres. In: Unlocking the Secrets of White Dwarf Stars. Astronomers' Universe. Springer, Cham. https://doi.org/10.1007/978-3-319-09369-7_17
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