Holdsworth, D and Kurtz, D and Smalley, B and Saio, H and Handler, G and Murphy, S and Lehmann, H (2016) HD 24355 observed by the Kepler K2 mission: a rapidly oscillating Ap star pulsating in a distorted quadrupole mode. Monthly Notices of the Royal Astronomical Society, 462 (1). 876 - 892. ISSN 1365-2966

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We present an analysis of the first Kepler K2 mission observations of a rapidly oscillating Ap (roAp) star, HD 24355 (V = 9.65). The star was discovered in SuperWASP broad-band photometry with a frequency of 224.31 d−1 (2596.18 μHz; P = 6.4 min) and an amplitude of 1.51 mmag, with later spectroscopic analysis of low-resolution spectra showing HD 24355 to be an A5 Vp SrEu star. The high-precision K2 data allow us to identify 13 rotationally split sidelobes to the main pulsation frequency of HD 24355. This number of sidelobes combined with an unusual rotational phase variation show this star to be the most distorted quadrupole roAp pulsator yet observed. In modelling this star, we are able to reproduce well the amplitude modulation of the pulsation, and find a close match to the unusual phase variations. We show this star to have a pulsation frequency higher than the critical cut-off frequency. This is currently the only roAp star observed with the Kepler spacecraft in short cadence mode that has a photometric amplitude detectable from the ground, thus allowing comparison between the mmag amplitude ground-based targets and the μmag spaced-based discoveries. No further pulsation modes are identified in the K2 data, showing this star to be a single-mode pulsator.

Item Type: Article
Uncontrolled Keywords: asteroseismology; techniques: photometric; stars: chemically peculiar; stars: individual: HD 24355; stars: magnetic field; stars: oscillations
Subjects: Q Science > QB Astronomy
Divisions: Faculty of Natural Sciences > School of Physical and Geographical Sciences
Depositing User: Symplectic
Date Deposited: 15 Aug 2016 09:23
Last Modified: 15 Aug 2016 09:23
URI: http://eprints.keele.ac.uk/id/eprint/2104

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