2021ApJS..253...26Y

Simultaneous monitoring observations of H₂O 6_1,6 - 5_2,3 and SiO v = 1, 2, J = 1 - 0, v = 1, J = 2 - 1, J = 3 - 2 masers were performed toward the suspected D-type symbiotic star V627 Cas from 2011 October to 2020 March using the Korean Very Long Baseline Interferometry (VLBI) Network (KVN) single-dish telescopes. All spectra of the H₂O masers showed highly redshifted emissions with respect to the stellar velocity of -52 km s^–1 with high asymmetries. In addition, the spectra of the H₂O maser showed three components which varied according to observational dates. On the other hand, the SiO v = 1, 2, J = 1 - 0 and v = 1, J = 2 - 1 masers exhibited a predominantly blueshifted emission in most epochs. The SiO v = 1, J = 3 - 2 maser has arisen around the stellar velocity from 2016 November 19 and shows a predominantly redshifted emission from 2018 June 15. We analyze time variations of the H₂O and SiO maser intensities, their intensity ratios, peak and mean velocities, and full width zero power. Based on these analyses, the asymmetries of the H₂O and SiO masers' spectra in V627 Cas and the variation characteristics of the maser properties of the different maser lines are discussed. As a possible cause of asymmetries, the influence of a hot component located at the eastern part of the red giant can be suggested based on the KVN VLBI results. The differences in the variation characteristics of the maser properties may originate from the differences in their locations and excitation conditions.