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Nonradial Pulsation among δ Scuti Stars

Published online by Cambridge University Press:  15 February 2018

Michel Breger
Michel Breger*
Affiliation:
Institute of Astronomy, University of Vienna, Austria

Abstract

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The review examines recent observational and theoretical results on the nonradial pulsation of δ Scuti stars. The dominant pulsation modes are rotationally split p modes with = 1 and 2, and radial orders 1 to 4. Line-profile analyses also reveal the existence of additional high-degree modes. Nonradial pulsation is usually accompanied by slow amplitude and period variability. The small-amplitude single-mode variables are shown to be typical nonradial pulsators.

The interesting cases of 1 Mon and θ2 Tau are examined in more detail. The present status of asteroseismolgy of the δ Scuti stars is reviewed.

The periods of the four evolved δ Scuti variables studied are found to be decreasing, although stellar evolution predicts period increases due to larger radii. New work on the multiple periods of AI Vel shows that, apart from stellar evolution, an additional mechanism must exist to cause temporary period changes. It is argued that for a larger sample of stars the average period change must nevertheless reflect evolutionary changes.

Type
Stellar Seismology
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 135 - 143
Copyright
Copyright © Cambridge University Press 1993

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