Observations of H2O Maser Sources in Nearby Molecular Clouds with VERA

Abstract

We presented the first results of multi-epoch VLBI observations of H2O maser sources in nearby molecular clouds with VERA. Observed sources were SVS13A in NGC1333, TMR-1 in the Taurus Molecular Cloud, Orion KL, HH1, and Mon R2 in the Orion-Monoceros Molecular Cloud Complex. Using the VERA dual-beam receiving system (Honma et al. 2003), we carried out phase-referencing VLBI and measured absolute proper motion and annual parallax of H2O maser features. We successfully detected the annual parallax of Orion KL, 2.4 ± 0.4 mas, corresponding to the distance of 410 ± 50 pc from the Sun (Fig. 1). In addition, the annual parallax of SVS13A was also determined to be 4.4 ± 0.9 mas (230 ± 50 pc), although the life time of the maser feature was only 100 days. We will continue monitoring observations of these sources with VERA to determine their annual parallax more precisely.