wra 1484 is an enigmatic object. it is a strong source at near- and far-infrared wavelengths. the optical spectrum is dominated by low excitation permitted and forbidden lines of feii. it is the central star of a bipolar shaped reflection nebula with a size of 15 arcseconds. the de-reddened colours, the extinction free continuum in the uv, as observed by iue, and the strength of the uv and optical emission lines of h, feii and mgii h and k, suggest a high photospheric temperature, from an analysis of the iras lrs database, we found that wra 1484 exhibits the well-known 21 micron feature in emission. it proves hard to determine the nature of the object, but a reasonable explanation for wra 1484 can be found in the late stages of stellar evolution of low mass stars; considering its spectral type and the presence of an infrared excess it could very well be a post-asymptotic giant branch (post-agb) object that is just in the phase of the ionization of its circumstellar shell. in this case, the object is of importance to stellar evolutionary models; over the last years a large number of candidate post-agb stars has been proposed in the literature. most of these are however cool stars, their spectral types peak in the range g-f while the minority of post-agb candidate stars are of b type. we propose to obtain iso sws spectra to study the infrared spectrum of wra 1484. modelling the uv, optical and infrared spectra with a photo-ionization code will enable us to constrain the parameters that govern the excitation conditions in the circumstellar envelope. in particular, we want to test the hypothesis that wra 1484 is in fact a post-agb star by comparing observations of its 21 micron feature with those of hii regions, and carbon-rich post-agb stars as listed in the central program.
Instrument
SWS01
Temporal Coverage
1996-09-10T20:04:23Z/1996-09-10T21:08:55Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
