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Radial Velocities of SS Cygni

Published online by Cambridge University Press:  12 April 2016

R. J. Stover
R. J. Stover*
Affiliation:
McDonald Observatory and Department of Astronomy, University of Texas at Austin

Extract

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SS Cygni was found by Joy (1956) to be a spectroscopic binary with an orbital period of about 6-1/2 hours. At minimum light it has mv=12 and is the brightest member of the dwarf nova class of variables. The minimum light spectrum reveals faint, narrow absorption lines of a G- or K-type star along with strong, broad emission lines of hydrogen, helium, and calcium which are produced by an accretion disk surrounding a white dwarf star. Joy’s radial velocities were not very accurate. Nevertheless, he was able to estimate the orbital elements, finding 115 km/s for the absorption line K-velocity and 122 km/s for the emission line K-velocity. In addition, he derived an orbital period of 0276244. Later minimum light observations by Walker and Chincarini (1968) were too few to be able to improve the orbital elements. Kiplinger (1979) refined the emission line radial velocities but was not able to remeasure the faint absorption line spectrum. This paper presents new radial velocity measurements of both the emission and absorption line spectra of SS Cygni at minimum light, and is the first thorough investigation of this star’s radial velocity variations in more than 20 years. The accuracy of the radial velocity curves has been greatly improved. We also find that Joy’s orbital period is in error by nearly two minutes.

Type
Colloquium Session VII
Information
International Astronomical Union Colloquium , Volume 53: White Dwarfs and Variable Degenerate Stars , August 1979 , pp. 489 - 493
Copyright
Copyright © The University of Rochester 1979

References

Joy, A. J. 1956, Ap. J., 124, 317.CrossRefGoogle Scholar
Kiplinger, A.L. 1979, A. J., 84, 655.CrossRefGoogle Scholar
Tull, R. G., Vogt, S. S. and Kelton, P. W. 1979, Proc. S.P.I.E. 172.Google Scholar
Walker, M. F. and Chincarlni, G. 1968, Ap. J., 154, 157.CrossRefGoogle Scholar