Pulsation and rotation of Kepler stars in the NGC 6866 field

Abstract

We present an analysis of stars in the field of the open cluster NGC 6866 (age 650 Myr) using data from the Kepler Input Catalogue (KIC) and time series photometry from the Kepler data base. We identify 31 δ Scuti and 8 γ Doradus pulsating variables as well as 23 red giants with solar-like oscillations. There are 4 eclipsing binaries and 106 stars showing rotational modulation indicative of starspots. We attempted to identify cluster members using their proper motions but found very poor discrimination between members and non-members. The KIC shows a concentration of stars with distance modulus V0 − MV = 10.47 ± 0.02. We used assumed radial modes in 9 δ Sct stars to determine their asteroseismic luminosities and found that the distance modulus falls within three narrow ranges depending on the assignment of overtone number. One of these ranges coincides with the KIC distance modulus. The rotation periods of main-sequence stars are correlated with colour, so that a period–age–mass relation can be derived from open clusters and applied to stars of unknown ages. Surprisingly, we find that the correlation applies not only to cool stars, but extends to A-type stars in the cluster. Finally, we present measurements of solar-like oscillations in red giants, a few of which might be cluster members.