Rotation and oblique pulsation in Kepler observations of the roAp star KIC 10483436

Abstract

Photometry of KIC 10483436 was obtained continuously with 1-min exposures over a 27-d period from the Kepler satellite. The light curve shows rotational variations from surface spots with a period of 4.303 [plus or minus] 0.002 d, an amplitude of about 6 mmag and eight pulsation frequencies typical of roAp stars. The high-frequency pattern consists of a quintuplet of equally spaced peaks where the frequency of the dominant central peak (68 [micro]mag amplitude) is 1353.00 [micro]Hz (P = 12.32 min). A second set of three peaks of lower amplitude are also visible. These appear to form part of a quintuplet centred on 1511.6 [micro]Hz with the central peak and one side peak missing. The equidistant frequency spacing is 2.69 [micro]Hz, which corresponds to the 4.303 d rotation period. However, the amplitudes (12 [micro]mag) of these peaks are too close to the detection level to allow definite identification of the multiplets. Although no spectrum is available, the character of the pulsations shows that this is a roAp star with two high-frequency modes modulated in amplitude in accordance with the oblique pulsator model. The 4.303-d variation in the light curve, which is interpreted as rotational modulation, shows harmonics as high as the 26th. These harmonics are probably a result of many patches of varying surface brightness associated with surface abundance variations characteristic of Ap stars.