On the analysis of band 3 of the ISO-SWS calibration sources

Abstract

We analyse ISO-SWS 01 (R ∼ 1500) 12-27.5 μm (band 3) spectra of the 10 standard calibration stars with the highest flux using synthetic spectra generated from (MARCS) atmosphere models. The comparison between the observed and synthetic spectra reveals the quality of (1) the atmospheric model construction and subsequent synthetic spectra computation and of (2) the (OLP 10.1) calibration and data reduction of the spectrometer at these wavelengths.

The models represent the general features of the observations, but the synthetic spectrum computation is hampered by the lack of comprehensive molecular and atomic line lists. We also suspect some problems with the temperature distribution in the outer layers of the model and inaccuracies in the extrapolation of the collision-induced absorption coefficients of H₂ pairs. We detect baseline ripples and fringes in the observed spectra, that survive the calibration and detailed reduction process. Photometric calibration uncertainties are estimated by means of the scaling factors between the synthetic and observed spectra.

Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries France, Germany, The Netherlands and the UK) and with the participation of ISAS and NASA.