Asymmetric distributions of H2O and SiO masers towards V627 Cas

Abstract

We performed simultaneous observations of the H 2 O 6 1,6 − 5 2,3 (22.235080 GHz) and SiO v=1, 2, J=1→0, SiO v=1, J=2→1, 3→2 (43.122080, 42.820587, 86.243442, and 129.363359 GHz) masers toward the suspected D-type symbiotic star, V627 Cas, using the Korean VLBI Network (KVN). Here, we present astrometrically registered maps of the H 2 O and SiO v=1, 2, J=1→0, SiO v=1, J=2→1 masers for five epochs from Jan. 2016 to Jun. 2018. Distributions of the SiO maser spots do not show clear ringlike structures, and those of the H 2 O maser are biased towards the north-northwest to west with respect to the SiO maser features according to observational epochs. These asymmetric distributions of H 2 O and SiO masers are discussed based on two scenarios of a bipolar outflow and the presence of the hot companion, a white dwarf, in V627 Cas. We carried out ring fitting of SiO v=1, and v=2 masers and estimated the expected position of the cool red giant. The ring radii of the SiO v=1 maser are slightly larger than those of the SiO v=2 maser, as previously known. Our assumption for the physical size of the SiO maser ring of V627 Cas to be the typical size of a SiO maser ring radius (∼ 4 AU) of red giants yields the distance of V627 Cas to be ∼ 1 kpc.