Title:	HD 12098: a highly distorted dipole mode in an obliquely pulsating roAp star
Authors:	Kurtz, D.W. Saio, H Holdsworth, D.L. Joshi, S Seetha, S
Issue Date:	9-Feb-2024
Publisher:	Oxford University Press for the Royal Astronomical Society
Citation:	Monthly Notices of the Royal Astronomical Society, Vol. 529, p556
Abstract:	HD 12098 is a rapidly oscillating Ap star pulsating in the most distorted dipole mode yet observed in this class of star. Using Transiting Exoplanet Survey Satellite (TESS) Sector 58 observations, we show that there are photometric spots at both the magnetic poles of this star. It pulsates obliquely primarily in a strongly distorted dipole mode with a period of Ppuls = 7.85 min (νpuls = 183.34905 d−1; 2.12210 mHz) that gives rise to an unusual quadruplet in the amplitude spectrum. Our magnetic pulsation model cannot account for the strong distortion of the pulsation in one hemisphere, although it is successful in the other hemisphere. There are high-overtone p modes with frequencies separated by more than the large separation, a challenging problem in mode selection. The mode frequencies observed in the TESS data are in the same frequency range as those previously observed in ground-based Johnson B data, but are not for the same modes. Hence the star has either changed modes, or observations at different atmospheric depth detect different modes. There is also a low-overtone p mode and possibly g modes that are not expected theoretically with the >1 kG magnetic field observed in this star.
Description:	Open Access
URI:	http://hdl.handle.net/2289/8258
Alternative Location:	https://ui.adsabs.harvard.edu/abs/2024MNRAS.529..556K/abstract https://arxiv.org/abs/2402.06314 https://doi.org/10.1093/mnras/stae431
Copyright:	2024 The Author(s)
Appears in Collections:	Research Papers (A&A)

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