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

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

Corresponding author: B. Vandenbussche, Bart.Vandenbussche@ster.kuleuven.ac.be

Received: 11 March 2002
Accepted: 15 May 2002

Abstract

We present an atlas of near-infrared spectra (2.36 μm–4.1 μm) of ~300 stars at moderate resolution (λ/–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 μm–4.05 μm 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, H₂O, NH, OH, SiO, HCN, C₂H₂, ...) 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. [CITE]) and late-type stars (Vandenbussche et al., in prep).