Publication
The Astrometric Animation of Water Masers toward the Mira Variable BX Cam
Publisher:
American Astronomical Society
Date:
12-2022
DOI:
10.3847/1538-4357/AC9599
Abstract: We report very long baseline interferometry (VLBI) monitoring observations of the 22 GHz water (H 2 O) masers around the Mira variable BX Cam, which were carried out as a part of the EAVN Synthesis of Stellar Maser Animations project. Data of 37 epochs in total were obtained from 2018 May to 2021 June with a time interval of 3–4 weeks, spanning approximately three stellar pulsation periods ( P = ∼440 days). In particular, the dual-beam system equipped on the VERA stations was used to measure the kinematics and parallaxes of the H 2 O maser features. The measured parallax, π = 1.79 ± 0.08 mas, is consistent with Gaia EDR3 and previously measured VLBI parallaxes within a 1 σ error level. The position of the central star was estimated, based on both the Gaia EDR3 data and the center position of the ring-like 43 GHz silicon-monoxide (SiO) maser distribution imaged with the Korean VLBI Network. The three-dimensional H 2 O maser kinematics indicates that the circumstellar envelope is expanding at a velocity of 13 ± 4 km s −1 , while there are asymmetries in both the spatial and velocity distributions of the maser features. Furthermore, the H 2 O maser animation achieved by our dense monitoring program manifests the propagation of shock waves in the circumstellar envelope of BX Cam.