Multi-site photometric campaign on the high amplitude {\delta} Scuti star KIC 6382916

TL;DR

This study presents a comprehensive multi-site photometric and spectroscopic analysis of the high-amplitude { extdelta} Scuti star KIC 6382916, identifying pulsation modes and comparing observations with theoretical models, revealing discrepancies in predicted frequency ranges.

Contribution

First detailed multi-site campaign combining Kepler data, ground-based multicolor photometry, and spectroscopy to analyze pulsation modes of KIC 6382916.

Findings

Identified three independent pulsation frequencies with dominant modes at 4.9107 and 6.4314 d$^{-1}$

Mode identification suggests l=1 for the two dominant modes, but uncertain for the third

Models fail to reproduce the low frequency of 4.9107 d$^{-1}$, indicating limitations in current pulsation theories.

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.