Rotational splitting and asteroseismic modelling of the delta Scuti star EE Camelopardalis

Abstract

According to the rotational splitting law of g modes, the frequency spectra of EE Cam can be disentangled only with oscillation modes of $\ell$ = 0, 1, and 2. Fifteen sets of rotational splits are found, containing five sets of $\ell =1$ multiplets and ten sets of $\ell =2$ multiplets. The rotational period of EE Cam is deduced to be $P_{\mathrm{rot}}$ = $1.84_{-0.05}^{+0.07}$ days. When we do model fittings, we use two nonradial oscillation modes ($f_{11}$ and $f_{32}$) and the fundamental radial mode $f_1$. The fitting results show that ${\chi }^2$ of the best-fitting model is much smaller than those of other theoretical models. The physical parameters of the best-fitting model are $M$ = 2.04 $M_{\odot }$, $Z=0.028$, $T_{\mathrm{eff}}$ = 6433 K, $\log L/L_{\odot }$ = 1.416, $R$ = 4.12 $R_{\odot }$, $\log g$ = 3.518, and ${\chi }^2$ = 0.00035. Furthermore, we find $f_{11}$ and $f_{32}$ are mixed mode, which mainly characterize the features of the helium core. The fundamental radial mode $f_1$ mainly restrict the features of the stellar envelope. Finally, the acoustic radius ${\tau }_0$ and the period separation ${\Pi }_0$ are determined to be 5.80 hr and 463.7 s respectively, and the size of the helium core of EE Cam is estimated to be $M_{\mathrm{He}}$ = 0.181 $M_{\odot }$ and $R_{\mathrm{He}}$ = 0.0796 $R_{\odot }$.

arXiv comment9 pages, 5 figures, 4 tables. accepted for publication in The Astrophysical Journal

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