Journal Article

Variability in mode amplitudes in the rapidly oscillating Ap star HR 1217

T. R. White, T. R. Bedding, D. Stello, D. W. Kurtz, M. S. Cunha and D. O. Gough

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 415, issue 2, pages 1638-1646
Published in print August 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18814.x
Variability in mode amplitudes in the rapidly oscillating Ap star HR 1217

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HR 1217 is one of the best studied rapidly oscillating Ap stars with eight known oscillation modes that are distorted by a strong, global magnetic field. We have reanalysed the multisite observations of HR 1217 taken in 1986 and 2000. We determined a weighting scheme for the 1986 and 2000 data to minimize the noise level. A wavelet analysis of the data has found that the modulation of the amplitude due to rotation for all frequencies is, in general, consistent with the expected modulation for modified ℓ= 1, 2 or 3 modes. Unexpected variations in the rotational modulation are also seen, with variations in the modulation profile, time of maximal pulsation and pulsational energy in each mode. Interestingly, these changes take place on a short time-scale, of the order of days. We consider potential explanations for these behaviours.

Keywords: stars: individual: HR 1217; stars: oscillations

Journal Article.  5760 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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