B. Vandenbussche 1, L. Waters 2, A. Heras 3, P. Morris 2, P. Sprengers 2, & Christoffel Waelkens 1 et al.
1 Institute of Astronomy K.U.Leuven, Celestijnenlaan 200 B, B-3001 Leuven, Belgium
After the liquid Helium of ISO depleted, the temperature of the focal plane remained low enough to operate the InSb band 1 detectors of the Short-Wavelength Spectrometer (SWS). The time available before and during the engineering test programme was used to record spectra of 300 stars between 2.36 and 4.05 microns at a resolution of 2000. The aim of the the programme was to extend the MK spectral classification scheme to the near infrared.
The targets observed cover the the entire MK classification scheme, allowing to refine the MK classification based on the near-infrared fingerprint of the stars. For late type stars, the spectral region between 2.36 and 4.05 shows many important molecular bands that will constrain the spectral type better than optical spectra. For hot stars the HI lines of the Bracket, Pfund and Humphreys series and the HeI and HeII lines are very sensitive to temperature, gravity and the signature of the outer layers of the star, like presence of outflows and winds.
The resulting catalogue of the programme will be very useful for stellar population synthesis studies of distant stellar systems. At infrared wavelengths these objects emit the integrated light of all stars in the system. A database of high resolution infrared spectra will allow to characterize the stellar population of such systems.
We will present the programme, an overview of the programme stars and the first calibrated spectra. Some examples will illustrate where the MK spectral classification can be refined with near-infrared spectra.