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Astron. Astrophys. 332, 25-32 (1998)

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1. Introduction

Searches for Asymptotic Giant Branch (AGB) stars in the Magellanic Clouds (MCs) have been made using optical spectroscopic surveys (e.g. Blanco et al. 1980, Blanco & McCarthy 1991, Rebeirot et al. 1993 [RAW], Morgan & Hatzidimitriou 1995), photometric surveys using V and I Schmidt plates (e.g. Reid et al. 1987) and optical surveys for LPVs (e.g. Payne-Gaposhkin 1971; Hughes 1989). However, these surveys missed the red dust-enshrouded OH/IR stars and infrared carbon stars in the MCs, very luminous examples of which did turn up in the IRAS point source catalog. Recently, near-infrared studies have been initiated to study IRAS sources in the MCs (Reid et al. 1990, Reid 1991, Wood et al. 1992 [W92], Zijlstra et al. 1996 [Z96], Loup et al. 1997, Tanabé et al. 1997). Still, most work until now focussed on the Large Magellanic Cloud. The existing data on IRAS selected AGB star candidates in the SMC can be found in Whitelock et al. (1989, WFMC), Wood et al. (1992) and Z96. As the metallicity difference between the SMC and our Galaxy is much larger than that between the LMC and our Galaxy, the SMC AGB stars are interesting in the study of the influence of metallicity on AGB evolution. As an example of this, Groenewegen et al. (1995) compared the spectral energy distribution and 8-13 µm spectra of an AGB star of comparable pulsation period in the galaxy, LMC and SMC and showed that the dust optical depth of the LMC star was two-thirds of that of the Galactic one, but that of the SMC star only one-fifteenth.

In this paper a sample of about 30 red candidate AGB stars in the SMC is selected for which JHK and partly L photometry is obtained. For a subsample optical spectroscopy is presented. In future papers additional ground-based and ISO observations will be presented.

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© European Southern Observatory (ESO) 1998

Online publication: March 10, 1998