ASTEROSEISMIC FUNDAMENTAL PROPERTIES OF SOLAR-TYPE STARS OBSERVED BY THE NASA KEPLER MISSION

Abstract

We use asteroseismic data obtained by the NASA Kepler mission to estimate the fundamental properties of more than 500 main-sequence and sub-giant stars. Data obtained during the first 10 months of Kepler science operations were used for this work, when these solar-type targets were observed for one month each in survey mode. Stellar properties have been estimated using two global asteroseismic parameters and complementary photometric and spectroscopic data. Homogeneous sets of effective temperatures, T eff , were available for the entire ensemble from complementary photometry; spectroscopic estimates of T eff and [Fe/H] were available from a homogeneous analysis of ground-based data on a subset of 87 stars. We adopt a grid-based analysis, coupling six pipeline codes to 11 stellar evolutionary grids. Through use of these different grid-pipeline combinations we allow implicitly for the impact on the results of stellar model dependencies from commonly used grids, and differences in adopted pipeline methodologies. By using just two global parameters as the seismic inputs we are able to perform a homogenous analysis of all solar-type stars in the asteroseismic cohort, including many targets for which it would not be possible to provide robust estimates of individual oscillation frequencies (due to a combination of low signal-to-noise ratio and short dataset lengths). The median final quoted uncertainties from consolidation of the grid-based analyses are for the full ensemble (spectroscopic subset) approximately 10.8% (5.4%) in mass, 4.4% (2.2%) in radius, 0.017 dex (0.010 dex) in log g, and 4.3% (2.8%) in mean density. Around 36% (57%) of the stars have final age uncertainties smaller than 1 Gyr. These ages will be useful for ensemble studies, but should be treated carefully on a star-bystar basis. Future analyses using individual oscillation frequencies will offer significant improvements on up to 150 stars, in particular for estimates of the ages, where having the individual frequency data is most important.

Synergies Between Asteroseismology and Exoplanetary Science

“…This is particularly valuable since the ∆ ν scaling relation has found widespread use for calculating stellar properties for thousands of stars in the era of "ensemble asteroseismology" (Kallinger et al, 2010;Chaplin et al, 2014). Figure 6 shows a comparison of the mean stellar density calculated from the ∆ ν scaling relation and from dynamically measured densities from double-lined eclipsing binaries (Frandsen et al, 2013;Gaulme et al, 2016), interferometric orbits (Procyon and α Cen A+B; see Bruntt et al, 2010, and references therein), as well as transiting exoplanets with known eccentricities: HD 17156 ; (Southworth, 2012;Huber et al, 2013a).…”

Asteroseismic age determination for dwarfs and giants

“…These quantities are related to the surface gravity and mean stellar density (Brown et al 1991;Ulrich 1986), and thus form the basis of the asteroseismic scaling relations: Fractional uncertainties in stellar properties determined using Bayesian schemes and the global seismic parameters. Results for 87 dwarfs and subgiants analysed by Chaplin et al (2014).…”

“…In order to determine ages for stars using the global seismic parameters, BASTA and BeSPP compare these quantities and the atmospheric parameters to those predicted by grids of models. Figure 1 shows the results obtained for the sample of 87 dwarfs and subgiants from Chaplin et al (2014) where spectroscopic T eff and [Fe/H] are available, resulting in median uncertainties of ∼2.2%, ∼5.5%, and ∼25% in radius, mass, and age respectively (see Fig. 1).…”

“…This opens the exciting possibility of accurately characterising stellar populations in different regions of the Milky Way to constraint the history of formation and evolution of our Galaxy (e.g., Casagrande et al 2014;Miglio et al 2013). Of particular importance in this endeavour are precise age determinations for large cohorts of dwarfs and giants (Casagrande et al 2015;Chaplin et al 2014), which can further help the usual kinematic and chemical dissection of the Galactic disc which has so far driven most of the comparisons between observations and simulations of our Galaxy (e.g., Adibekyan et al 2012;Edvardsson et al 1993;Haywood et al 2013;Schönrich & Binney 2009, just to name a few).…”

On the mass estimation for FGK stars: comparison of several methods

“…This technique can result in mass uncertainties below 5 per cent if a few frequencies with an uncertainty below 0.1 µHz are available (e.g. Kjeldsen, Bedding & Christensen-Dalsgaard 2009;Huber et al 2012;Mathur et al 2012;Creevey et al 2013;Chaplin et al 2014 and references therein). The main drawback for this is the fact that the number of stars that fulfil the above precision in frequencies is still small.…”