KIC 6951642: confirmed Kepler $\gamma$ Doradus-$\delta$ Scuti star with intermediate to fast rotation in a possible single-lined binary system

Abstract

KIC 6951642 has been reported as a candidate hybrid pulsator of type-$\gamma$ Doradus-$\delta$ Scuti from observations of the first quarters of the Kepler mission. We aim to investigate the pulsating nature of KIC 6951642 and to search for the signature of rotation and/or activity in the light curves. We performed an iterative frequency search of both Fourier spectra, and searched for regular patterns in them. We applied spectrum synthesis to determine the atmospheric stellar parameters. Since KIC 6951642 was reported to belong to a spectroscopic binary system, we fitted the time delays derived from the light curves with the radial velocities obtained from published as well as new spectra in an attempt to improve the quality of the first orbit. Follow-up spectroscopy showed that KIC 6951642 is a fast-rotating F0-type star in a possible single-lined binary with a period of $\sim$4.8 yr. In the low-frequency regime, we identified the frequencies of 0.721 d${}^{-1}$ as well as of 0.0087 d${}^{-1}$. We attribute the first frequency to stellar rotation and the second one to stellar activity with a cycle. We also detected $g$ modes, with the strongest mode located at 2.238 d${}^{-1}$, as well as three asymmetric multiplets (with a mean spacing of 0.675$\pm$0.044 d${}^{-1}$). In the high-frequency regime, we detected frequencies of type-$\delta$ Scuti, with the strongest mode located at 13.96 d${}^{-1}$, as well as seven asymmetric multiplets (with a mean spacing of 0.665$\pm$0.084 d${}^{-1}$). We subsequently identified a few more frequencies that appear to be combinations of a $g$ or $p$ mode and one of the higher cited frequencies not due to pulsations. We propose that KIC 6951642 accommodates for a fast-rotating $\gamma$ Dor-$\delta$ Sct hybrid star with various rotationally split multiplets of $g$ and $p$ modes and that it also displays a cycle lasting years of (possible) stellar activity.

References in corpus (15)

• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Modern stellar spectroscopy caveats
• CoRoT reveals a magnetic activity cycle in a Sun-like star
• The first view of $\delta$ Scuti and $\gamma$ Doradus stars with the TESS mission
• Finding binaries from phase modulation of pulsating stars with Kepler: V. Orbital parameters, with eccentricity and mass-ratio distributions of 341 new binaries
• The role of turbulent pressure as a coherent pulsational driving mechanism: the case of the delta Scuti star HD 187547
• Regular patterns in the acoustic spectrum of rapidly rotating stars
• The effect of tides on near-core rotation: analysis of 35 Kepler $\gamma$ Doradus stars in eclipsing and spectroscopic binaries
• Precise surface gravities of $\delta$ Scuti stars from asteroseismology
• A comparison of the dynamical and model-derived parameters of the pulsating eclipsing binary KIC9850387
• Eclipsing Systems with Pulsating Components (Types β Cep, δ Sct, γ Dor or Red Giant) in the Era of High-Accuracy Space Data
• $\gamma$ Doradus Pulsations in the Eclipsing Binary Star KIC 6048106
• KIC~8975515: a fast-rotating ($\gamma$ Dor - $\delta$ Sct) hybrid star with Rossby modes and a slower $\delta$ Sct companion in a long-period orbit

Cited by in corpus (1)

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