Abstract
Abstract In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from Kepler space photometry with high-resolution spectroscopy of the High Efficiency and Resolution Mercator Échelle Spectrograph mounted on the Mercator telescope. The fundamental atmospheric parameters, radial velocities, rotation velocities, and elemental abundance for Fe and Li were determined by analyzing line strengths and fitting-line profiles, based on a 1D local thermodynamic equilibrium model atmosphere. Second, we analyzed a photometric light curve obtained by Kepler and we extracted asteroseismic data of this target using Lets Analysis, Use and Report of Asteroseismology, a new seismic tool developed for the study of evolved FGK solar-like stars. We determined the evolutionary status and effective temperature, surface gravity, metallicity, microturbulence, and chemical abundances for Li, Ti, Fe, and Ni for HD 226808, by employing spectroscopy, asteroseismic scaling relations, and evolutionary structure models built in order to match observed data. Our results also show that an accurate synergy between good spectroscopic analysis and asteroseismology can provide a jump toward understanding evolved stars.
Highlights
Red giants are cool evolved stars with an extended convective envelope, which can, as in main sequence solarlike stars, stochastically excite modes of oscillation
In order to clarify the properties of the secondary clump star HD 226808 (KIC 5307747), we combined four years of data from the Kepler space photometry with the high-resolution spectroscopy of the HERMES spectrograph mounted on the Mercator telescope
We analyzed photometric light curve obtained by Kepler and we extracted asteroseismic data of this target by using LAURA (Lets Analysis, Use and Report of Asteroseismology), a new seismic tool developed for the study of evolved FGK solar-like stars
Summary
Red giants are cool evolved stars with an extended convective envelope, which can, as in main sequence solarlike stars, stochastically excite modes of oscillation. Red clump stars are natural standard candles (Stanek et al 1998; Hawkins et al 2017), while regular RGB stars or more massive secondary RC stars of nearly the same effective temperatures (Teff ) are not In this context, finding and characterizing core helium burning RC stars is very important to fine tune stellar evolution and Galactic archeology, and for building a precise cosmic distance ladder (Stanek et al 1998; Bressan et al 2013; Bovy et al 2014; Gontcharov 2017; Hawkins et al 2017). We use photometric data from Kepler space telescope and HERMES ground-based high-resolution spectroscopy to produce a deep analysis of the bright red-giant star HD 226808 (KIC 530774) This star is one of three brightest classified as secondary clump star and observed by Kepler on long cadence mode (Mosser et al 2014).
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