2018ApJ...866..147C

We have computed a grid of theoretical models to fit the 12 oscillation modes of HIP 80088 observed by K2. HIP 80088 is determined to be a pre-main-sequence star, in which the CN cycle has not arrived at the equilibrium state. Mass fractions of C12 and N14 in metal composition are 0.1277_–0.0049^+0.0064 and 0.1092_–0.0074^+0.0057, respectively, indicating that 28% of C12 have turned into N14. Meanwhile, our fitting results show that physical parameters of HIP 80088 converge to a small range: M = 1.68-1.78 M_☉, Z = 0.015-0.018, υ_e=120–136 km s^–1, log g = 4.114-4.125, R = 1.882-1.914 R_☉, τ₀ = 7636-7723 s, and age = 9.03-10.21 Myr. Based on our model fittings, f₃ is suggested to be one radial mode, f₂, f₄, f₈, and f₁₁ to be four l = 1 modes, and f₁, f₅, f₆, f₇, f₉, f₁₀, and f₁₂ to be seven l = 2 modes. In particular, we find that (f₂, f₄, f₈) form one complete triplet with the averaged frequency spacing of 16.045 µHz, and (f₅, f₇, f₉, f₁₀) form four components of one quintuplet with the averaged frequency spacing of 13.388 µHz. The two averaged frequency spacings are not equal. Based on the best-fitting model, those l = 2 modes of HIP 80088 are found to be mixed modes, which are p-dominated modes with pronounced g-mode features, while oscillation modes with l = 1 are p modes.