G 207-9 and LP 133-144: light-curve analysis and asteroseismology of two ZZ Ceti stars

G 207-9 and LP 133-144 are two rarely observed ZZ Ceti stars located in the middle and close to the blue edge of the ZZ Ceti instability domain, respectively. We aimed to observe them at least during one observing season at Konkoly Observatory with the purpose of extending the list of known pulsation modes for asteroseismic investigations and detect any significant changes in their pulsational behaviour. We determined five and three new normal modes of G 207-9 and LP 133-144, respectively. In LP 133-144, our frequency analysis also revealed that at least at three modes there are actually triplets with frequency separations of ∼ 4 μHz. The rotational period of LP 133-144 based on the triplets is ≃42 h. The preliminary asteroseismic fits of G 207-9 predict T_eff = 12 000 or 12 400 K and M_{ast }=0.855-0.870 M_{⊙} values for the effective temperature and mass of the star, depending on the assumptions on the spherical degree (l) values of the modes. These results are in agreement with the spectroscopic determinations. In the case of LP 133-144, the best-fitting models prefer T_eff = 11 800 K in effective temperature and M_* ≥ 0.71 M_⊙ stellar masses, which are more than 0.1 M_⊙ larger than the spectroscopic value.