Poster abstract details

We report measurements of the trigonometric parallx of H2O masers around the protoplanetary nebula OH 231.8+4.2 carried out with the Very Long Baseline Array. Based on astrometric monitoring for 1 year, we measured a trigonometric parallax of 0.89 ± 0.02 mas, corresponding to a distance of 1.12 +0.04/-0.03 kpc. This is most accurate distance to OH 231.8+4.2, and the first one based on an annual parallax measurement. Combining the distance and proper motions with observed radial velocities gives the full space motion of OH231.8+4.2. The distribution and internal motions of the H2O masers are consistent with the bipolar outflow in literatures. We also present our observations of SiO masers, which trace the disk of OH 231.8+4.2.