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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, D. O. Gough

Abstract
HR1217 is one of the best-studied rapidly oscillating Ap (roAp) 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 timescale, of the order of days. We consider potential explanations for these behaviours.

Keywords
stars: individual: HR 1217 - stars: oscillations

Monthly Notices of the Royal Astronomical Society
Volume 415, Issue 2, Page 1638
2011 August

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia