KIC 7582608: a new Kepler roAp star with frequency variability
1 Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
2 Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE, UK
3 Centro de Astrofísca e Faculdade de Ciências, Universidade do Porto, Rua das Estrelas, P-4150-762 Porto, Portugal
4 Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
a e-mail: email@example.com
Published online: 23 September 2015
We analyse the fifth roAp star reported in the Kepler field, KIC 7582608, discovered with the SuperWASP project. The object shows a high frequency pulsation at 181.7324d−1 (P = 7.9 min) with an amplitude of 1.45 mmag, and low frequency rotational modulation corresponding to a period of 20.4339 d. Spectral analysis confirms the Ap nature of the target, with characteristic lines of rare earth elements present. From our spectral observations we derive a lower limit on the mean magnetic field modulus of 〈B〉 =3.05 ± 0.23 kG. Long Cadence Kepler observations show a frequency quintuplet split by the rotational period of the star, typical for an oblique pulsator. We suggest the star is a quadrupole pulsator with a geometry such that i ~ 66° and β ~ 33°. We detect frequency variations of the pulsation in both the WASP and Kepler data sets on many time scales. Linear, non-adiabatic stability modelling allows us to constrain a region on the HR diagram where the pulsations are unstable, an area consistent with observations.
© Owned by the authors, published by EDP Sciences, 2015
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