Annual Parallax Distance and Kinematical Property of H2O Masers in IRAS 19312+1950

• Published in: Publications of the Astronomical Society of Japan Vol. 63; no. 1; pp. 81 - 87
• Main Authors: Imai, Hiroshi, Tafoya, Daniel, Honma, Mareki, Hirota, Tomoya, Miyaji, Takeshi
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford University Press 25.02.2011
• Subjects: stars: AGB and post-AGB; stars: individual (IRAS 19312 + 1950; masers
• ISSN: 0004-6264; 2053-051X
• DOI: 10.1093/pasj/63.1.81

We report on results of astrometric observations of H $_{2}$ O masers in the pre-planetary nebula candidate source IRAS 19312 $+$ 1950 with the VLBI Exploration of Radio Astrometry (VERA), yielding an annual parallax, $\pi$ $=$ 263 $\ \pm\ $ 47 $\ \mu$ as, and a secular motion, ( $\mu_{\alpha}$ , $\mu_{\delta}$ ) $=$ ( $-$ 2.61 $\ \pm\ $ 0.47, $-$ 6.73 $\ \pm\ $ 0.14) [mas yr $^{-1}$ ], for IRAS 19312 $+$ 1950. We then derived a heliocentric distance of $D$ $=$ 3.80 $^{+0.83}_{\-0.58}\ $ kpc, a location in the Galaxy ( $R$ , $z$ ) $=$ (7.07 $\ \pm\ $ 0.12 kpc, 28 $\ \pm\ $ 3 pc), and a three-dimensional velocity vector ( $V_{R}$ , $V_{\theta}$ , $V_{z}$ ) $=$ (33 $\ \pm\ $ 28, 214 $\ \pm\ $ 4, $-$ 14 $\ \pm\ $ 8) [km s $^{-1}$ ] in galactic cylindrical coordinates. Based on these parameters, we discuss the intrinsic properties of IRAS 19312 $+$ 1950. We estimated the mass of the central star to be $\sim\ $ 8 $\ M_{\odot}$ and the deviation of the source motion from the circular galactic rotation to be $\sim\ $ 40 km s $^{-1}$ . These are consistent with this source being an intermediate-mass late AGB or early post-AGB star.