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Astron. Astrophys. 339, 134-140 (1998)

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1. Introduction

We present the results of imaging spectroscopy of the pre-main-sequence star HD 97300, obtained with the infrared camera (ISOCAM, Cesarsky et al. 1996a) and circular variable filter wheel on board of the infrared space observatory (ISO, Kessler et al., 1996). The data presented here are the first results of a program aimed at investigating the nature of the mid-infrared emission associated to Herbig AeBe stars. The young star HD 97300 is located in the Chamalion I cloud (Whittet et al. 1997), at distance [FORMULA] 188 pc. The star excites the prominent reflection nebulosity Ced 112. Its spectral type has been estimated to be B9 (Rydgren 1980) and its luminosity [FORMULA]35 [FORMULA] (van den Ancker et al., 1997). Its pre-main-sequence evolutionary status (i.e., its classification among Herbig AeBe stars, or HAeBe) is based on indirect clues, namely the association with a reflection nebulosity, the presence of an infrared excess at [FORMULA] µm, and its location on the ZAMS in the HR diagram (Whittet et al. 1997). There is no evidence of significant infrared excess at wavelengths shorter than [FORMULA]5 µm nor of H[FORMULA] emission (Thé et al. 1986). HD 97300 is very likely a relatively old object among HAeBe stars, representative of the latest stages of the pre-main-sequence evolution.

We report the detection of an extended, ring-like structure around HD 97300, whose emission is dominated by the infrared emission bands at 6.2, 7.7, 8.7, 11.3 and 12.5 µm, (hereafter IEBs), observed in our own and other galaxies wherever neutral matter is exposed to UV radiation (see for example, the review by Allamandola et al. 1989 and the many papers presenting CVF and SWS spectra in the special issue of Astronomy and Astrophysics on ISO published in November 1996).

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© European Southern Observatory (ESO) 1998

Online publication: September 30, 1998