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Influence of Rotation on the Stellar Parameters

Published online by Cambridge University Press:  12 April 2016

V. Wenske  and
D. Schönberner
V. Wenske
Affiliation:
Institut für Theor. Physik und Sternwarte der Universität Kiel Olshausenstr. 40, W-2300 Kiel, Germany
D. Schönberner
Affiliation:
Institut für Theor. Physik und Sternwarte der Universität Kiel Olshausenstr. 40, W-2300 Kiel, Germany

Extract

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For several years it has become quite common to derive stellar parameters like effective temperature, Teff, and surface acceleration, g, by means of properly calibrated photometric indices, and to use these values for the derivation of important properties of stellar aggregates (viz. ages, star formation history, distances, etc.). Photometric observations, however, fail to give informations about one important property of a star: its rotational rate!

The main effect of rotation is to increase the size of the star, mainly in the equatorial region, leading to lower surface temperatures and accelerations. Since in non–spherical stars Teff and g depend on the latitude, the observed values, which are, of course, averages over the visible hemisphere, depend on the angle of inclination, i. Collins & Sonneborn (1977) utilized the rigidly rotating stellar models of Sackmann and Anand (1970) to compute emergent fluxes and photometric indices for various stellar masses, inclination angles i and rotational parameters being the break–up rotational rate. These indices, viz. C0 and β, represent then averages over the visible part of the rotally distorted stellar models. Closer inspections indicated also that emergent fluxes and line profiles of rotationally distorted stars can be matched by the predictations of standard model atmospheres to a very high accuray, even for w close to unity (Wenske 1992, Diplom Thesis).

Type
II. Atmospheres, a window to the interior
Information
International Astronomical Union Colloquium , Volume 137: Inside the Stars , 1993 , pp. 162 - 164
Copyright
Copyright © Astronomical Society of the Pacific 1993

References

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