http://arxiv.org/abs/1604.00613
Asteroseismology is an unique and powerful tool to detect the internal structure of stars. CBS 114 is the sixth known pulsating DBV star. It was observed by Handler, Metcalfe, \& Wood at South African Astronomical Observatory over 3 weeks in 2001. Then, it was observed by Metcalfe et al. at Bohyunsan Optical Astronomy Observatory and McDonald Observatory respectively for 7 nights in 2004. Totally 2 triplets, 4 doublets, and 5 singlets were identified. The frequency splitting values are very different, from 5.2 $\mu$Hz to 11.9 $\mu$Hz, which may reflect differential rotations. We evolve grids of white dwarf models by \texttt{MESA}. Cores, added with He/C envelopes, of those white dwarf models are inserted into \texttt{WDEC} to evolve grids of DBV star models. With those DBV star models, we calculate eigenperiods. Those calculated periods are used to fit observed periods. A best-fitting model is selected. The parameters are $T_{eff}$ = 25000 K, $M_{*}$ = 0.740 $M_{\odot}$, and log($M_{He}/M_{*}$) = -4.5. With the massive stellar mass, the effective temperature is close to previous spectroscopic result. In addition, kinetic energy distributions are calculated for the best-fitting model. We find that the observed modes with large frequency splitting values are fitted by the calculated modes with much kinetic energy distributed in C/O core. After preliminary analysis, we suggest that the C/O core may rotate at least 2 times faster than the helium layer for CBS 114.
Y. Chen
Tue, 5 Apr 16
48/67
Comments: 11pages,5figures,accepted by Research in Astronomy and Astrophysics on 2016/04/01
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