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T.B. O'Hara, M. Meixner, A.K. Speck, T. Ueta (Univ. of Illinois, Urbana-Champaign), M. Bobrowsky (Challenger Center)
We present new imaging of the dust shell surrounding IRAS 18184-1623 (HD 168625). This object has a warm (Tdust ~ 200K) bipolar dust shell surrounding a star of temperature Teff ~ 12,000K. On the basis of its small-amplitude photometric variations on time scales of weeks, its high-velocity wind, and its ringlike nebula, 18184 has been classified as a low-luminosity luminous blue variable (LBV), currently in a quiescent state. We present here imaging from the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on HST and far-infrared imaging from ISOPHOT. These images are compared with previously obtained mid-infrared images to refine the morphology of the nebula and to examine temperature gradients in the dust shell. We also present preliminary radiative transfer modeling results, which are compared with a previously obtained spectral energy distribution for 18184, leading to refined constraints on stellar parameters and nebula morphology.
This work has been supported by NSF AST 97-33697, NASA JPL 961504, and NASA STI 7898.02-96A.