Asteroseismology of KIC 11754974: a high-amplitude SX Phe pulsator in a 343-d binary system

Murphy, S. J. and Pigulski, A. and Kurtz, D. W. and Suarez, J. C. and Handler, G. and Balona, L. A. and Smalley, B. and Uytterhoeven, K. and Szabó, Róbert and Thygesen, A. O. and Elkin, V. and Breger, M. and Grigahcene, G. and Guzik, J. and Handler, G. and Nemec, J. M. and Southworth, J. (2013) Asteroseismology of KIC 11754974: a high-amplitude SX Phe pulsator in a 343-d binary system. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 432 (3). pp. 2284-2297. ISSN 0035-8711

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Abstract

The candidate SX Phe star KIC 11754974 shows a remarkably high number of com- bination frequencies in the Fourier amplitude spectrum: 123 of the 166 frequencies in our multi-frequency fit are linear combinations of independent modes. Predictable patterns in frequency spacings are seen in the Fourier transform of the light curve. We present an analysis of 180 d of short-cadence Kepler photometry and of new spectro- scopic data for this evolved, late A-type star. We infer from the1150-d, long-cadence light curve, and in two different ways, that our target is the primary of a 343-d, non-eclipsing binary system. According to both methods, the mass function is simi- lar, f (M ) = 0.0207 ± 0.0003 M⊙. The observed pulsations are modelled extensively, using separate, state-of-the-art, time-dependent convection (TDC) and rotating mod- els. The models match the observed temperature and low metallicity, finding a mass of 1.50–1.56 M⊙. The models suggest the whole star is metal-poor, and that the low metallicity is not just a surface abundance peculiarity. This is the best frequency anal- ysis of an SX Phe star, and the only Kepler δ Sct star to be modelled with both TDC and rotating models.

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