Holdsworth, DL, Saio, H, Bowman, DM, Kurtz, DW, Sefako, RR, Joyce, M, Lambert, T and Smalley, B (2018) Suppressed phase variations in a high amplitude rapidly oscillating Ap star pulsating in a distorted quadrupole mode. Monthly Notices of the Royal Astronomical Society, 476 (1). pp. 601-616. ISSN 1365-2966

 Preview
Text
B Smalley - Suppressed phase variations in a high amplitude rapidly osciallating....pdf - Published Version

## Abstract

We present the results of a multisite photometric observing campaign on the rapidly oscillating Ap (roAp) star 2MASS 16400299-0737293 (J1640; $V=12.7$). We analyse photometric $B$ data to show the star pulsates at a frequency of $151.93$ d$^{-1}$ ($1758.45 \mu$Hz; $P=9.5$ min) with a peak-to-peak amplitude of 20.68 mmag, making it one of the highest amplitude roAp stars. No further pulsation modes are detected. The stellar rotation period is measured at $3.6747\pm0.0005$ d, and we show that rotational modulation due to spots is in anti-phase between broadband and $B$ observations. Analysis and modelling of the pulsation reveals this star to be pulsating in a distorted quadrupole mode, but with a strong spherically symmetric component. The pulsational phase variation in this star is suppressed, leading to the conclusion that the contribution of $\ell>2$ components dictate the shape of phase variations in roAp stars that pulsate in quadrupole modes. This is only the fourth time such a strong pulsation phase suppression has been observed, leading us to question the mechanisms at work in these stars. We classify J1640 as an A7 Vp SrEu(Cr) star through analysis of classification resolution spectra.

Item Type: Article This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. asteroseismology, techniques: photometric, stars: chemically peculiar, stars: individual: J1640, stars: magnetic field, stars: oscillations Q Science > QB Astronomy Faculty of Natural Sciences > School of Chemical and Physical Sciences Author Symplectic 28 Mar 2018 09:17 02 May 2018 08:54 http://eprints.keele.ac.uk/id/eprint/4652