* Astronomy

Title: Asteroseismology of KIC 11754974: a high-amplitude SX\,Phe pulsator in a 343-day binary system
Authors: S. J. Murphy, A. Pigulski, D.W. Kurtz, J.C. Suarez, G. Handler, L.A. Balona, B. Smalley, K. Uytterhoeven, R. Szabo, A.O. Thygesen, V. Elkin, M. Breger, A. Grigahcene, J.A. Guzik, J.M. Nemec, J. Southworth

The candidate SX Phe star KIC 11754974 shows a remarkably high number of combination 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 spectroscopic data for this evolved, late A-type star. We infer from the 1150-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 similar, f(M)=0.0207 ± 0.0003 solar masses. The observed pulsations are modelled extensively, using separate, state-of-the-art, time-dependent convection (TDC) and rotating models. The models match the observed temperature and low metallicity, finding a mass of 1.50-1.56 solar masses. 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 analysis of an SX Phe star, and the only Kepler \delta\ Sct star to be modelled with both TDC and rotating models.

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