THE PHYSICAL PARAMETERS OF THE RETIRED A STAR HD?185351

摘要

We report here an analysis of the physical stellar parameters of the giant star HD?185351 using Kepler short-cadence photometry, optical and near infrared interferometry from CHARA, and high-resolution spectroscopy. Asteroseismic oscillations detected in the Kepler short-cadence photometry combined with an effective temperature calculated from the interferometric angular diameter and bolometric flux yield a mean density ρ = 0.0130 ± 0.0003 ρ☉ and surface gravity log g = 3.280 ± 0.011. Combining the gravity and density we find R = 5.35 ± 0.20 R ☉ and M = 1.99 ± 0.23 M ☉. The trigonometric parallax and CHARA angular diameter give a radius R = 4.97 ± 0.07 R ☉. This smaller radius, when combined with the mean stellar density, corresponds to a stellar mass 1.60 ± 0.08 M ☉, which is smaller than the asteroseismic mass by 1.6σ. We find that a larger mass is supported by the observation of mixed modes in our high-precision photometry, the spacing of which is consistent only for M 1.8 M ☉. Our various and independent mass measurements can be compared to the mass measured from interpolating the spectroscopic parameters onto stellar evolution models, which yields a model-based mass M , model = 1.87 ± 0.07 M ☉. This mass agrees well with the asteroseismic value, but is 2.6σ higher than the mass from the combination of asteroseismology and interferometry. The discrepancy motivates future studies with a larger sample of giant stars. However, all of our mass measurements are consistent with HD?185351 having a mass in excess of 1.5 M ☉.