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

Smalley, B. and Niemczura, E. and Murphy, S. J. and Lehmann, H. and Kurtz, D. W. and Holdsworth, D. L. and Cunha, M. S. and Balona, L. A. and Briquet, M. and Bruntt, H. and De Cat, P. and Lampens, P. and Thygesen, A. O. and Uytterhoeven, K. (2015) KIC 4768731: a bright long-period roAp star in the Kepler field. Monthly Notices of the Royal Astronomical Society, 452 (4). pp. 3334-3345. ISSN 0035-8711

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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.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: File reproduced in accordance with the copyright policy of the publisher/author.
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 28 Apr 2022 01:57
Last Modified: 28 Apr 2022 01:57
Uncontrolled Keywords: Asteroseismology; Stars: abundances; Stars: chemically peculiar; Stars: individual: KIC 4768731; Stars: oscillations; Techniques: photometric; Astrophysics - Solar and Stellar Astrophysics
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
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