The Kepler Cepheid V1154 Cyg revisited: light curve modulation and detection of granulation
Derekas, A; Plachy, E; Molnár, L; Sódor, Á; Benkő, JM; Szabados, L; Bognár, Zs; Csák, B; Szabó, GyM; Szabó, R
WoS ID: 000393647100022
Scopus ID: 85008900263
We present a detailed analysis of the bright Cepheid-type variable star V1154 Cygni using 4 years of continuous observations by the Kepler space telescope. We detected 28 frequencies using standard Fourier transform method. We identified modulation of the main pulsation frequency and its harmonics with a period of ∼159 d. This modulation is also present in the Fourier parameters of the light curve and the O–C diagram. We detected another modulation with a period of about 1160 d. The star also shows significant power in the low-frequency region that we identified as granulation noise. The effective timescale of the granulation agrees with the extrapolated scalings of red giant stars. Non-detection of solar-like oscillations indicates that the pulsation inhibits other oscillations. We obtained new radial velocity observations which are in a perfect agreement with previous years data, suggesting that there is no high mass star companion of V1154 Cygni. Finally, we discuss the possible origin of the detected frequency modulations.