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Astron. Astrophys. 330, L17-L20 (1998)

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2. Observations

For all stars in our sample of AGB stars we have full-grating ISO/SWS spectra with complete wavelength coverage from 2-45 µm (AOT01, speed 1 or 2) and on average a spectral resolution of 250. Recently, we acquired in our open time program high-resolution SWS spectra (AOT06) for a selected number of O-rich AGB stars with the 13 µm dust feature at the full-grating resolution of 1500 in the wavelength range 12-16.5 µm. For one star, W Hya, we obtained in addition a SWS Fabry-Perot measurement with a resolution of 30 000, centered on the emission line at 13.87 µm.

The data were reduced using the SWS Interactive Analysis (SIA) data reduction software package using standard ISO pipeline data products (version 6.0). Although in principle flux levels may be affected by the uncertainty in the dark current measured during the observation, the high flux levels of our stars ensure that this effect can be neglected here. The main uncertainties in the observed flux come from the pointing uncertainty and the relative spectral response function (RSRF). The latter also introduces a few artifacts in the spectrum and some instrumental fringing between 12 and 16.5 [FORMULA] m. The flux level of the Fabry-Perot observation is scaled to the flux of the grating spectrum.

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© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998