Determining stellar parameters of asteroseismic targets: going beyond the use of scaling relations

Abstract

Asteroseismic parameters allow us to measure the basic stellar properties of field giants observed far across the Galaxy. Most of such determinations are, up to now, based on simple scaling relations involving the large frequency separation, ∆ν, and the frequency of maximum power, ν max . In this work, we implement ∆ν and the period spacing, ∆P , computed along detailed grids of stellar evolutionary tracks, into stellar isochrones and hence in a Bayesian method of parameter estimation. Tests with synthetic data reveal that masses and ages can be determined with typical precision of 5 and 19 per cent, respectively, provided precise seismic parameters are available. Adding independent information on the stellar luminosity, these values can decrease down to 3 and 10 per cent respectively. The application of these methods to NGC 6819 giants produces a mean age in agreement with those derived from isochrone fitting, and no evidence of systematic differences between RGB and RC stars. The age dispersion of NGC 6819 stars, however, is larger than expected, with at least part of the spread ascribable to stars that underwent mass-transfer events.

Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

“…12 we show the values of log g derived with StePar against those obtained adopting the distances from Gaia DR2 (Gaia Collaboration et al 2018), if available, and the Hipparcos mission (van Leeuwen 2007). We computed the latter log g values by means of the PARAM web interface 8 (da Silva et al 2006;Rodrigues et al 2014Rodrigues et al , 2017, which employs a Bayesian approach to derive the stellar parameters, including stellar age, mass and radius. The log g values obtained with PARAM can be found in Tables A2 and A3.…”

Empirical Relations for the Accurate Estimation of Stellar Masses and Radii

“…The most significant contributions come from Eker et al (2014), with 222 stars, and Serenelli et al (2017), with 397 stars. The MS/post-MS classification was done using the evolutionary tracks described in Rodrigues et al (2017), with solar metallicity. The impact of this classification in our results, when tracks with other characteristics are used, is analyzed in Section 5.3.…”

“…There, we explained that we used the evolutionary tracks with solar metallicity described in Rodrigues et al (2017) for this classification. The observational classification of a star as MS or post-MS is not a trivial task.…”

“…We have used tracks described in Rodrigues et al (2017) using the same physics, but with different metallicities in a range Z=[0.00176, 0.0553]. In addition, we have also used tracks that include diffusion and also cover a wider range of metallicities, in the range Z=[0.00002, 0.06215].…”

Scaling Relations for Solar-Like Oscillations: A Review

“…However, they do represent an empirical fit optimised to the data obtained from stellar models that include canonical stellar physics. Serenelli et al (2017) formulated a calibration factor to account for the surface effects in cases where ∆ν in stellar models is computed from theoretical frequencies (e.g., Sharma et al, 2016;Rodrigues et al, 2017). The advantage of relying on ∆ν freq computed from theoretical frequencies is that it captures deviations from the pure scaling relation due to the detailed structure of stellar models (e.g., Belkacem et al, 2013).…”