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

Abstract

Abstract 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.