Is one month of observations enough? A case study on Kepler-21

We present the asteroseismic analysis of Kepler observations of the bright oscillating star Kepler‐21 (KIC 3632418, KOI 975, HD 179070). The pulsation modes exhibited by this star are similar to the acoustic p‐modes seen in our Sun. The analysis of observations covering a time period of 460 days has showed that the star hosts a small planet (Kepler‐21b), which has a mass of ∼10 MEarth, a radius of 1.64±0.04 REarth and a revolving period of 2.8 days (Howell et al. 2012). Our current work deals with the comparison of p‐mode frequency estimation using 1 and 10 months of observations (Quarter 2.3 and Quarters 5 through 7) of this F5 subgiant (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)