We have computed a grid of theoretical models to fit the twelve oscillation modes of HIP 80088 observed by K2. HIP 80088 is determined to be a pre-main sequence star, in which CN cycle has not arrived at the equilibrium state. Mass fractions of C12 and N14 in metal composition are 0.1277$^{ +0.0064}_{ -0.0049}$ and 0.1092$^{ +0.0057}_{ -0.0074}$ respectively, indicating that twenty-eight percent 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 $M _{ \odot}$, $Z$ = 0.015$-$0.018, $\upsilon_{ \rm e}$ = 120$-$136 km s$^{ -1}$, $\log g$ = 4.114$-$4.125, $R$ = 1.882$-$1.914 $R_{ \odot}$, $\tau_{ 0}$ = 7636$-$7723 s, and age = 9.03$-$10.21 Myr. Based on our model fittings, $f_{ 3}$ is suggested to be one radial mode, $f_{ 2}$, $f_{ 4}$, $f_{ 8}$, and $f_{ 11}$ to be four $\ell$ = 1 modes, and $f_{ 1}$, $f_{ 5}$, $f_{ 6}$, $f_{ 7}$, $f_{ 9}$, $f_{ 10}$, and $f_{ 12}$ to be seven $\ell$ = 2 modes. In particularly, we find that ($f_{ 2}$, $f_{ 4}$, $f_{ 8}$) form one complete triplet with the averaged frequency spacing of 16.045 $\mu$Hz , and ($f_{ 5}$, $f_{ 7}$, $f_{ 9}$, $f_{ 10}$) form four components of one quintuplet with the averaged frequency spacing of 13.388 $\mu$Hz. The two averaged frequency spacings are not equal. Based on the best-fitting model, those $\ell$ = 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 $\ell$ = 1 are p modes.
Categories: astro-ph.SR