# MAPPING OBSERVATIONS OF AN UNUSUAL SIO MASER SOURCE, IRAS $19312+1950$

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 Title: MAPPING OBSERVATIONS OF AN UNUSUAL SIO MASER SOURCE, IRAS $19312+1950$ Creators: Nakashima, Jun-Ichi; Deguchi,Shuji; Kuno, Nario Issue Date: 2004 Publisher: Ohio State University Abstract: IRAS $19312+1950$ is an SiO maser source that exhibits a prominent nebulosity and rich-molecular species. Though SiO maser sources are mostly identified as a late-type star with active mass-loss, the kind of this object is unclear. To reveal the true character of IRAS $19312+1950$, mapping observations of this object were made in the $CO J = 1 - 0, ^{13}CO J = 1 - 0, C^{18}O J = 1 - 0, CS J = 2 - 1$, and HCN $J = 1 - 0$ lines and in the 150 GHz continuum band using the Nobeyama 45m telescope. The line profiles of the $^{12}CO$ and HCN spectra consists of a weak component with the width of $50 km s^{-1}$ and a strong component of the width of 3 km $s^{-1}$. The profile of the $^{13}CO, C^{18}O$, and CS lines have only the narrow component. Both of the components have an intensity peak at the IRAS position. The narrow component was clearly resolved with a $15^{\prime \prime}$ telescope beam. The spectral energy distribution of this object exhibits a doubly peaked profile between 1 and $25 \mu$m. The 150 GHz continuum flux density was found to be 0.07 Jy, which is consistent with the flux density predicted by the expanding envelope model with a mass loss rate of ${\sim} 10^{-4} M_{\odot} yr^{-1}$ at a distance of 2.5 kpc. Though the present observations do not preclude the possibility of a young stellar object, we suggest that IRAS 19312+1950 is an AGB/post-AGB star. In addition to the results of single dish observations, we report a preliminary result of recent mapping observations in the $HCO^{+} J = 1 - 0$ line with the Berkeley-Illinois-Maryland-Association (BIMA) Millimeter Array. In the $HCO^{+}$ spectrum, both of the strong-narrow and weak-broad components were confirmed. And then, in the integrated intensity map of $HCO^{+}$, we clearly found a bipolar flow, which corresponds the red- and blue-shift wings of the broad component. Description: The Graduate University for Asvanced Studies, Nobeyama Radio Observatroy, Minamimaki, Minamisaku, Nagano 384-1305, Japan. Author Institution: Department of Astronomy, University of Illinois at Urbana-Champaign; Department of Astronomy, Nobeyama Radio Observatory, National Astronomical Observatory URI: http://hdl.handle.net/1811/21284 Other Identifiers: 2004-RD-11