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Mode Determination by Fourier Analysis of Line-Profile Variations: Application to τ Peg

Published online by Cambridge University Press:  15 February 2018

E.J. Kennelly ,
G.A.H. Walker ,
W.J. Merryfield  and
J.M. Matthews
E.J. Kennelly
Affiliation:
University of British Columbia
G.A.H. Walker
Affiliation:
University of British Columbia
W.J. Merryfield
Affiliation:
University of Victoria
J.M. Matthews
Affiliation:
Université de Montréal

Abstract

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The identification of modes of oscillation is an important first step towards the seismology of stars. Low- and high-degree nonradial modes of oscillation may appear as variations in the line profiles of rapidly rotating δ Scuti stars. We present a technique whereby complex patterns in the line profiles are decomposed into Fourier components in both time and “Doppler space”. The technique is applied to the 7.3-hour time series of high-resolution data obtained from CFHT for the δ Scuti star τ Peg. In addition to the low-degree mode which has been identified in photometric studies (Breger 1991), we find evidence for at least three high-degree modes near 11 and 15. Correcting for the rotation of the star, most of these modes appear to oscillate with frequencies near 17 cycles day-1. Our results are found to be in good agreement with the theoretical limits imposed on the frequencies of oscillation by the models of Dziembowski (1990).

Type
Stellar Seismology
Information
International Astronomical Union Colloquium , Volume 139: New Perspectives on Stellar Pulsation and Pulsating Variable Stars , 1993 , pp. 147
Copyright
Copyright © Cambridge University Press 1993

References

Breger, M., 1991, Astron. Astrophys. 250, 107.Google Scholar
Dziembowski, W., 1990, in: Progress of Seismology of the Sun and Stars, eds. Osaki, Y. and Shibahashi, H., Lecture Notes in Physics 367, p 359.Google Scholar