Unusual high-frequency oscillations in the Kepler δ Scuti star KIC 4840675

August 2012 • 2012MNRAS.424.1187B

Authors • Balona, L. A. • Breger, M. • Catanzaro, G. • Cunha, M. S. • Handler, G. • Kołaczkowski, Z. • Kurtz, D. W. • Murphy, S. • Niemczura, E. • Paparó, M. • Smalley, B. • Szabó, R. • Uytterhoeven, K. • Christiansen, J. L. • Uddin, K. • Stumpe, M. C.

Abstract • We show that the star KIC 4840675 observed by Kepler is composed of three stars with a rapidly rotating A-type star and two solar-type fainter companions. The A-type star is a δ Scuti variable with a dominant mode and many other modes of lower amplitude, including several low-frequency variations. The low-frequency variation with highest amplitude can be interpreted as rotational modulation with the light curve changing with time. However, the most interesting aspect of this star is a triplet of independent modes in the range 118-129 d^-1 (1.4-1.5 mHz), which is far outside the range of typical δ Scuti frequencies. We discuss the possibility that these modes could be solar-like oscillations, oscillations of the roAp type or due to an unseen pulsating compact companion. Based on observations made with the Nordic Optical Telescope, operated jointly by Denmark, Finland, Iceland, Norway and Sweden, on the island of La Palma at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC).

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Jessie Christiansen

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