  We obtained H-band polarimetric data of IRAS 19312+1950 using the
near-infrared camera (CIAO) on the 8 m Subaru telescope. In order to
investigate the physical properties of the central star and the nebula, we
performed dust radiative transfer modeling and compared the model results with
the observed spectral energy distributions (SEDs), the radial profiles of the
total intensity image, and the fraction of linear polarization map. The total
intensity image shows a nearly spherical core with ~3" radius, an S-shaped arm
extending ~10" in the northwest to southeast direction, and an extended lobe
towards the southwest. The polarization map shows a centro-symmetric vector
alignment in almost the entire nebula and low polarizations along the S-shaped
arm. These results suggest that the nebula is accompanied by a central star,
and the S-shaped arm has a physically ring-like structure. From our radiative
transfer modeling, we estimated the stellar temperature, the bolometric
luminosity, and the current mass-loss rate to be 2800 K, 7000 L_sun, and
5.3x10^{-6} M_sun yr^{-1}, respectively. Taking into account previous
observational results, such as the detection of SiO maser emissions and
silicate absorption feature in the 10 $\mu$m spectrum, our dust radiative
transfer analysis based on our NIR imaging polarimetry suggests that (1) the
central star of IRAS 19312+1950 is likely to be an oxygen-rich, dust-enshrouded
AGB star and (2) most of the circumstellar material originates from other
sources (e.g. ambient dark clouds) rather than as a result of mass loss from
the central star.
