Frequency Identification and Asteroseismic Analysis of the Red Giant KIC 9145955: Fundamental Parameters and Helium Core Size

Abstract

We have analyzed 18 quarters of long-cadence data of KIC 9145955 provided by Kepler , and extracted 61 oscillation frequencies from these high-precision photometric data. The oscillation frequencies include 7 l  = 0 modes, 44 l  = 1 modes, 7 l  = 2 modes, and 3 l  = 3 modes. We identify l  = 0 modes as p modes and l  = 2 modes as p -dominated modes. For l  = 1 modes, all of them are identified as mixed modes. These mixed modes can be used to determine the size of the helium core. We conduct a series of asteroseismic models and the size of the helium core is determined to be M He  = 0.210 ± 0.002 M ⊙ and . Furthermore, we find that only the acoustic radius τ 0 can be precisely determined with the asteroseismic method independently. The value of τ 0 is determined to be 0.494 ± 0.001 days. By combining asteroseismic results and spectroscopic observations, we obtain the best-fittin g model. The physical parameters of this model are M  = 1.24 M ⊙ , Z  = 0.009, α  = 2.0, T eff  = 5069 K, log g = 3.029, R  = 5.636 R ⊙ , and L  = 18.759 L ⊙ . In addition, we think that the observed frequency F39 (96.397 μ Hz) is more appropriate to be identified as a mixed mode of the most p -dominated.