Asteroseismology of the ultramassive ZZ Ceti star WD 0246+326

The internal structures of pulsating white dwarfs can be explored only with asteroseismology. Time series photometric observations were made for the pulsating DA white dwarf (ZZ Ceti star) WD~0246+326 during 9 nights in 2014 with a bi-site observation campaign. Eleven frequencies were detected including 1 triplet, 2 doublets, and 4 single modes, which are identified as either $l=1$ or $l=2$ modes with the complementarity of frequencies present in the literature. From the multiplets, the rotation period of \astrobj{WD~0246+326} is derived as $3.78\pm 0.11$ days. The average period spacing of the l=1 modes $\mathrm{\Delta }P=29.3\pm 0.2s$, implies that \astrobj{WD~0246+326} may be a massive ZZ Ceti star concerning the $\mathrm{\Delta }P-M_{\ast }$ relationship for the DAVs. Preliminary analysis derives the stellar parameters of $M_{\ast }=0.98\pm 0.01$~${\mathrm{M}}_{\odot }$ and $T_{\mathrm{e}\mathrm{f}\mathrm{f}}=11700\pm 100$~K by fitting the theoretical frequencies of the eigen modes to the observed ones.