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 (38)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Stellar Multiplicity
• Gaia Early Data Release 3: The astrometric solution
• Mind your Ps and Qs: the Interrelation between Period (P) and Mass-ratio (Q) Distributions of Binary Stars
• HERMES: a high-resolution fibre-fed spectrograph for the Mercator telescope
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Gaia Data Release 2: Mapping the Milky Way disc kinematics
• The Kepler characterization of the variability among A- and F-type stars. I. General overview
• Modern stellar spectroscopy caveats
• Helium variation due to self-pollution among Globular Cluster stars: consequences on the horizontal branch morphology
• CoRoT reveals a magnetic activity cycle in a Sun-like star
• Gamma Doradus Stars: Defining a New Class of Pulsating Variables
• Hybrid gamma Doradus - delta Scuti pulsators: New insights into the physics of the oscillations from Kepler observations
• KIC 4544587: an Eccentric, Short Period Binary System with delta Sct Pulsations and Tidally Excited Modes
• Characterising the observational properties of δ Sct stars in the era of space photometry from the Kepler mission
• On the sensitivity of gravito-inertial modes to differential rotation in intermediate-mass main-sequence stars
• Turbulent convection and pulsation stability of stars - II. Theoretical instability strip for $\delta$ Scuti and $\gamma$ Doradus stars
• The first view of $\delta$ Scuti and $\gamma$ Doradus stars with the TESS mission
• Pulsation frequency distribution in Delta Scuti stars
• 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
• KIC 10080943: a binary star with two $\gamma$ Doradus/$\delta$ Scuti hybrid pulsators. Analysis of the g modes
• KIC 10080943: An eccentric binary system containing two pressure- and gravity-mode hybrid pulsators
• KIC 4142768: An Evolved Gamma Doradus/Delta Scuti Hybrid Pulsating Eclipsing Binary with Tidally Excited Oscillations
• 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
• Asteroseismology
• Multi-technique investigation of the binary fraction among A-F type candidate hybrid variable stars discovered by Kepler
• Tango of celestial dancers: A sample of detached eclipsing binary systems containing g-mode pulsating components. A case study of 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
• Determining the evolutionary stage of the delta Scuti star HIP 80088 with asteroseismology

Cited by in corpus (1)

• The phase curve of the ultra-hot Jupiter WASP-167b as seen by TESS