Multisite photometric campaign on the high-amplitude δ Scuti star KIC 6382916

Abstract

We present results of a multi-site photometric campaign on the high-amplitude $\delta$\,Scuti star KIC\,6382916 in the {\it Kepler} field. The star was observed over a 85-d interval at five different sites in North America and Europe during 2011. {\it Kepler} photometry and ground-based multicolour light curves of KIC\,6382916 are used to investigate the pulsational content and to identify the principal modes. High-dispersion spectroscopy was also obtained in order to derive the stellar parameters and projected rotational velocity. From an analysis of the {\it Kepler} time series, three independent frequencies and a few hundred combination frequencies are found. The light curve is dominated by two modes with frequencies $f_{1}$= 4.9107 and $f_{2}$= 6.4314\,d$^{-1}$. The third mode with $f_{3}$= 8.0350\,d$^{-1}$ has a much lower amplitude. We attempt mode identification by examining the amplitude ratios and phase differences in different wavebands from multicolour photometry and comparing them to calculations for different spherical harmonic degree, $l$. We find that the theoretical models for $f_1$ and $f_2$ are in a best agreement with the observations and lead to value of l = 1 modes, but the mode identification of $f_3$ is uncertain due to its low amplitude. Non-adiabatic pulsation models show that frequencies below 6\,d$^{-1}$ are stable, which means that the low frequency of $f_1$ cannot be reproduced. This is further confirmation that current models predict a narrower pulsation frequency range than actually observed.