12yr KVN obs. of SiO and H2O masers toward WX Ser

This study has been conducted with 21m single-dish radio telescopes of the Korean VLBI Network from 2009 June to 2021 June. Five maser lines were considered: SiO v=1,2, J=1-0; SiO v=1, J=2-1, 3-2; and H2O 6_1,6_-5_2,3_ transitions, with the SiO maser lines distributed near the stellar velocity and the H2O maser exhibiting an asymmetric line profile with five to six peaked components.

Intense H2O maser emissions suddenly appeared in 2019 September, indicating flaring. The intensity variations of SiO and H2O masers are strongly correlated with the optical light curve (OLC) of the central star, with individual phase lags; the phase lag of the H2O maser relative to the OLC is larger than that of the SiO masers. The consequent phase difference between the SiO masers and the H2O maser likely indicates that their formation regions and main driving mechanisms are different from each other.