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Astron. Astrophys. 362, 273-280 (2000)

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1. Introduction

IRAS 03201+5459 (hereafter IRAS 03201) was first detected by the IRAS satellite (see The IRAS Point Source Catalogue) (PSC 1988). Fluxes at 12 and 25 microns, [FORMULA] and [FORMULA], are 13.77 and 5.14 Jy, respectively, which are of good quality. The resulting color [FORMULA] is equal to -0.43 which is typical for a late-type star with a circumstellar envelope, possibly optically thin and warm if the star is located in region II, or cold if its IRAS 60 µm flux puts it in region VIa on the IRAS color-color diagram of van der Veen & Habing (1988). Due to the low quality of the IRAS flux at 60 µm (only upper limit values are available for the 60 and 100 µm fluxes) it is difficult to judge the properties of the object solely by its IRAS [FORMULA] color.

As the flux at 12 micron is relatively high, a Low Resolution Spectrum (LRS) between 7 and 23 µm was also obtained by IRAS. Based on a clear absorption feature around 10 µm it was classified as LRS 32 (Olnon et al. 1986). However, it is worth noting that Kwok et al. (1997) put this LRS spectrum into unusual (U) group according to a by eye classification scheme developed by Volk & Cohen (1989). It was assumed to be a carbon-rich source with silicate absorption due to interstellar extinction. This possibility will be discussed in more detail in Sect. 3.

After the discovery of this source during the IRAS mission, follow-up identification attempts were carried out, but no object from the existing catalogues was found to be associated with this source. An attempt at optical identification in POSS R plate gave a negative result (Jiang & Hu 1992), so the object is fainter than 21st magnitude in the R band. Moreover, there was no detection of the source in the near-infrared (IR) at the limit of magnitude 8 at K band, i.e. the flux at 2.2 µm is less than 0.4 Jy. The steep increase between the near-IR such as K band and the mid-IR (e.g. 12 µm) indicates strong emission in this range, for which an ISO Short Wavelength Spectrometer (SWS) observation was proposed. Searches for the molecular maser emissions from OH (Galt et al. 1989), H2O (Zuckerman & Lo 1987) and SiO (Jiang et al. 1996) all failed. In consequence, no more measurements were available prior to the Infrared Space Observatory (ISO) observations aside from the IRAS photometry and spectroscopy.

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© European Southern Observatory (ESO) 2000

Online publication: October 30, 19100
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