KIC 4768731: a bright long-period roAp star in the Kepler field

Smalley, B.; Niemczura, E.; Murphy, S.J.; Lehmann, H.; Kurtz, D.W.; Holdsworth, D.L.; Cunha, M.S.; Balona, L.A.; Briquet, M.; Bruntt, H.; De Cat, P.; Lampens, P.; Thygesen, A.O.; Uytterhoeven, K.

doi:10.1093/mnras/stv1515

KIC 4768731: a bright long-period roAp star in the Kepler field

Smalley, B.; Niemczura, E.; Murphy, S.J.; Lehmann, H.; Kurtz, D.W.; Holdsworth, D.L.; Cunha, M.S.; Balona, L.A.; Briquet, M.; Bruntt, H.; De Cat, P.; Lampens, P.; Thygesen, A.O.; Uytterhoeven, K.

Authors

Barry Smalley b.smalley@keele.ac.uk

E. Niemczura

S.J. Murphy

H. Lehmann

D.W. Kurtz

D.L. Holdsworth

M.S. Cunha

L.A. Balona

M. Briquet

H. Bruntt

P. De Cat

P. Lampens

A.O. Thygesen

K. Uytterhoeven

Abstract

We report the identification of 61.45?d-1 (711.2 µHz) oscillations, with amplitudes of 62.6 µmag, in KIC 4768731 (HD 225914) using Kepler photometry. This relatively bright (V = 9.17) chemically peculiar star with spectral type A5 Vp SrCr(Eu) has previously been found to exhibit rotational modulation with a period of 5.21?d. Fourier analysis reveals a simple dipole pulsator with an amplitude that has remained stable over a 4-yr time span, but with a frequency that is variable. Analysis of high-resolution spectra yields stellar parameters of Teff = 8100 ± 200 K, log?g = 4.0 ± 0.2, [Fe/H] = +0.31 ± 0.24 and v sin?i = 14.8 ± 1.6 km s-1. Line profile variations caused by rotation are also evident. Lines of Sr, Cr, Eu, Mg and Si are strongest when the star is brightest, while Y and Ba vary in antiphase with the other elements. The abundances of rare earth elements are only modestly enhanced compared to other roAp stars of similar Teff and log?g. Radial velocities in the literature suggest a significant change over the past 30 yr, but the radial velocities presented here show no significant change over a period of 4 yr.

Citation

Smalley, B., Niemczura, E., Murphy, S., Lehmann, H., Kurtz, D., Holdsworth, D., …Uytterhoeven, K. (2015). KIC 4768731: a bright long-period roAp star in the Kepler field. Monthly Notices of the Royal Astronomical Society, 452(4), 3334 - 3345. https://doi.org/10.1093/mnras/stv1515

Journal Article Type	Article
Acceptance Date	Jul 6, 2015
Online Publication Date	Aug 4, 2015
Publication Date	Oct 1, 2015
Journal	Monthly Notices of the Royal Astronomical Society
Print ISSN	0035-8711
Publisher	Oxford University Press
Peer Reviewed	Peer Reviewed
Volume	452
Issue	4
Pages	3334 - 3345
DOI	https://doi.org/10.1093/mnras/stv1515
Keywords	Solar and Stellar Astrophysics
Publisher URL	http://dx.doi.org/10.1093/mnras/stv1515