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

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IRAS 03201+5459: a C-rich AGB star with silicate absorption *

B.W. Jiang 1, R. Szczerba 2 and S. Deguchi 3

1 Beijing Astronomical Observatory, Chinese Academy of Sciences, Datun Rd. No.20(A), Beijing 100012, P.R. China
2 N. Copernicus Astronomical Center, ul. Rabiaska 8, 87-100 Toru, Poland
3 Nobeyama Radio Observatory, Minamimaki, Minamisaku, Nagano 384-1305, Japan

Received 20 March 2000 / Accepted 17 August 2000

Abstract

IRAS 03201+5459 is a late-type star with a circumstellar envelope according to its IRAS color. It has no identification at optical or near-infrared wavelengths. A full ISO-SWS spectrum between 2.3 and 43 µm was taken at a resolution of about [FORMULA]300 to investigate its nature. The spectrum shows the 9.7 µm feature in absorption, usually seen in O-rich envelopes, and the 3 µm feature in absorption which is related to C-rich late-type stars. Furthermore, modeling of the spectral energy distribution indicates the necessity of C-based dust. To understand these conflicting spectral features, we have estimated interstellar extinction in the direction of IRAS 03201+5459 by different methods. In no case can we get a sufficiently large [FORMULA] to explain the observed strength of the 9.7 µm absorption feature as due to interstellar extinction. Therefore, we investigated the hypothesis that a central C-rich star is surrounded by an inner C-rich shell and an outer O-rich shell (the object may be in the transition stage of evolution from an O-rich to a C-rich star). However, this require a very short lifetime of the object as a C-rich star, and then the similarity between IRAS and ISO spectra makes this hypothesis difficult to sustain. Alternatively O-rich material around the C-star IRAS 03201+5459 might be confined into more stationary disk-like configuration which is seen (almost) edge-on.

Key words: stars: AGB and post-AGB – stars: chemically peculiar – stars: circumstellar matter – stars: individual: IRAS 03201+5459

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with participation of ISAS and NASA

Send offprint requests to: B.W. Jiang (jiang@class1.bao.ac.cn)

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© European Southern Observatory (ESO) 2000

Online publication: October 30, 19100
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