Asteroseismology of KIC 7107778: a binary comprising almost identical subgiants

Abstract

We analyze an asteroseismic binary system: KIC 7107778, a non-eclipsing, unresolved target, with solar-like oscillations in both components. We used \emph{Kepler} short cadence time series spanning nearly two years to obtain the power spectrum. Oscillation mode parameters were determined using Bayesian inference and a nested sampling Monte Carlo algorithm with the \texttt{DIAMONDS} package. The power profiles of the two components fully overlap, indicating their close similarity. We modelled the two stars with \texttt{MESA} and calculated oscillation frequencies with \texttt{GYRE}. Stellar fundamental parameters (mass, radius and age) were estimated by grid modelling with atmospheric parameters and the oscillation frequencies of $l=0,2$ modes as constraints. Most $l=1$ mixed modes were identified with models searched using a bisection method. Stellar parameters for the two sub-giant stars are: $M_A=1.42\pm 0.06$ $M_{\astrosun}$, $M_B=1.39\pm 0.03$ $M_{\astrosun}$, $R_A=2.93\pm 0.05$ $R_{\astrosun}$, $R_B=2.76\pm 0.04$ $R_{\astrosun}$, $t_A=3.32\pm 0.54$ Gyr and $t_B=3.51\pm 0.33$ Gyr. The mass difference of the system is $\sim$1\%. The results confirm their simultaneous birth and evolution, as is expected from binary formation. KIC 7107778 comprises almost identical twins, and is the first asteroseismic sub-giant binary to be detected.

13 pages, 8 figures

References in corpus (15)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The connection between stellar granulation and oscillation as seen by the Kepler mission
• A new correction of stellar oscillation frequencies for near-surface effects
• Asteroseismology of the solar analogs 16 Cyg A & B from Kepler observations
• The LAMOST Stellar Parameter Pipeline at Peking University --- LSP3
• A precise asteroseismic age and radius for the evolved Sun-like star KIC 11026764
• DIAMONDS: a new Bayesian Nested Sampling tool. Application to Peak Bagging of solar-like oscillations
• Gaia Data Release 1, Pre-processing and source list creation
• Bayesian peak bagging analysis of 19 low-mass low-luminosity red giants observed with Kepler
• Finding binaries among Kepler pulsating stars from phase modulation of their pulsations
• Spectroscopic binaries with components of similar mass
• Oscillation mode linewidths and heights of 23 main-sequence stars observed by Kepler
• Deriving the orbital properties of pulsators in binary systems through their light arrival time delays
• Twins Among the Low Mass Spectroscopic Binaries

Cited by in corpus (5)

• Asteroseismology of 36 \emph{Kepler} subgiants -- I. Oscillation frequencies, linewidths and amplitudes
• A comparison of the dynamical and model-derived parameters of the pulsating eclipsing binary KIC9850387
• Seismic performance
• 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
• Two's a crowd? Characterising the effect of photometric contamination on the extraction of the global asteroseismic parameter ${\nu }_{\text{max}}$ in red-giant binaries