IRAS 19312+1950 is an SiO maser source that exhibits a prominent bipolar nebulosity .
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 .
Near-infrared imaging observations were also made in the J , H , and K -bands .
The line profiles of the ^ { 12 } CO and HCN spectra consist of a weak broad component with a line width of about 50 km s ^ { -1 } and a strong narrow component of the width of about 3 km s ^ { -1 } .
The profiles 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 } y ^ { -1 } at a distance of 2.5 kpc .
We argue that the broad component originates from the expanding envelope of this object , and that the hot dust cloud , which is the source of the narrow component , is also physically associated with this object .
Though the present observations do not preclude the possibility of a young stellar object , we argue that it is less plausible .
We conclude that IRAS 19312+1950 is an AGB/post-AGB star that is evolved from a massive progenitor .