Astronomy & Astrophysics

Free access article

A&A 390, 1033-1048 (2002)
DOI: 10.1051/0004-6361:20020767

The ISO-SWS post-helium atlas of near-infrared stellar spectra

B. Vandenbussche¹, D. Beintema², T. de Graauw², L. Decin¹, H. Feuchtgruber³, A. Heras⁴, D. Kester², F. Lahuis², A. Lenorzer⁵, R. Lorente⁶, A. Salama⁶, C. Waelkens¹, L. Waters^{1, 5} and E. Wieprecht³

¹ Instituut voor Sterrenkunde, K.U.Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
² SRON National Institute for Space Research, Groningen, The Netherlands
³ Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
⁴ Astrophysics Missions Division, Research and Scientific Support Department of ESA, ESTEC, PO Box 299, 2200 AG Noordwijk, The Netherlands
⁵ Sterrenkundig Instituut "Anton Pannekoek", Amsterdam, The Netherlands
⁶ ISO Data Center, Astrophysics Division of ESA, Villafranca del Castillo, Spain

(Received 11 March 2002 / Accepted 15 May 2002 )

Abstract
We present an atlas of near-infrared spectra (2.36 $\mu$ m-4.1 $\mu$ m) of ~300 stars at moderate resolution ( $\lambda$ / $\delta~\lambda \approx 1500$ -2000). The spectra were recorded using the Short-Wavelength Spectrometer aboard the Infrared Space Observatory (ISO-SWS). The bulk of the observations were performed during a dedicated observation campaign after the liquid helium depletion of the ISO satellite, the so-called post-helium programme. This programme was aimed at extending the MK-classification to the near-infrared. Therefore the programme covers a large range of spectral types and luminosity classes. The 2.36 $\mu$ m-4.05 $\mu$ m region is a valuable spectral probe for both hot and cool stars. H I lines (Bracket, Pfund and Humphreys series), He I and He II lines, atomic lines and molecular lines (CO, H ₂O, NH, OH, SiO, HCN, C ₂H ₂, ...) are sensitive to temperature, gravity and/or the nature of the outer layers of the stellar atmosphere (outflows, hot circumstellar discs, etc.). Another objective of the programme was to construct a homogeneous dataset of near-infrared stellar spectra that can be used for population synthesis studies of galaxies. At near-infrared wavelengths these objects emit the integrated light of all stars in the system. In this paper we present the dataset of post-helium spectra completed with observations obtained during the nominal operations of the ISO-SWS. We discuss the calibration of the SWS data obtained after the liquid helium boil-off and the data reduction. We also give a first qualitative overview of how the spectral features in this wavelength range change with spectral type. The dataset is scrutinised in two papers on the quantitative classification of near-infrared spectra of early-type stars (Lenorzer et al. 2002) and late-type stars (Vandenbussche et al., in prep).

Key words: stars: general -- infrared: stars -- atlases

Offprint request: B. Vandenbussche, Bart.Vandenbussche@ster.kuleuven.ac.be

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