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Orbits and pulsations of the classical zeta Aurigae binaries

Eaton, Joel A. and Henry, Gregory W. and Odell, Andrew P. (2008) Orbits and pulsations of the classical zeta Aurigae binaries. Astrophysical Journal, 679 (2). pp. 1490-1498. ISSN 1538-4357


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Publisher’s or external URL: http://dx.doi.org/10.1086/587452


We have derived new orbits for zeta Aur, 32 Cyg, and 31 Cyg with observations from the Tennessee State University (TSU) Automatic Spectroscopic Telescope, and used them to identify nonorbital velocities of the cool supergiant components of these systems. We measure periods in those deviations, identify unexpected long-period changes in the radial velocities, and place upper limits on the rotation of these stars. These radial-velocity variations are not obviously consistent with radial pulsation theory, given what we know about the masses and sizes of the components. Our concurrent photometry detected the nonradial pulsations driven by tides ( ellipsoidal variation) in both zeta Aur and 32 Cyg, at a level and phasing roughly consistent with simple theory to first order, although they seem to require moderately large gravity darkening. However, the K component of 32 Cyg must be considerably bigger than expected, or have larger gravity darkening than zeta Aur, to fit its amplitude. However, again there is precious little evidence for the normal radial pulsation of cool stars in our photometry. H alpha shows some evidence for chromospheric heating by the B component in both zeta Aur and 32 Cyg, and the three stars show among them a meager similar to 2-3 outbursts in their winds of the sort seen occasionally in cool supergiants. We point out two fundamental questions in the interpretation of these stars: (1) whether it is appropriate to model the surface brightness as gravity darkening and (2) whether much of the nonorbital velocity structure may actually represent changes in the convective flows in the stars' atmospheres.

Item Type: Article
Publisher’s Statement: © 2008 The American Astronomical Society. Published by IOP Publishing.
ID number or DOI: 10.1086/587452
Keywords: 32 cygni; 1982 eclipse; binaries : spectroscopic; cool giants; gamma-doradus; h-alpha line; k supergiants; nonradial pulsators; optical-spectra; red giants; stars : late-type; stars : oscillations; variable-stars
Subjects: Q Science > QB Astronomy
NAU Depositing Author Academic Status: Faculty/Staff
Department/Unit: College of Engineering, Forestry, and Natural Science > Physics and Astronomy
Date Deposited: 30 Sep 2015 04:46
URI: http://openknowledge.nau.edu/id/eprint/105

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