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

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

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.

Keywords
asteroseismology – binaries: spectroscopic – stars: individual: KIC 4840675 – stars: oscillations – stars: variables: δ Scuti

Monthly Notices of the Royal Astronomical Society
Volume 424, Issue 2, Page 1187
2012 August

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Instituto de AstrofĆ­sica e CiĆŖncias do EspaƧo Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
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