Astron. Astrophys. 357, 1013-1019 (2000)

2. Observations and reduction

We present observations taken with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO) (see Table 1). All spectra were taken using the AOT1 scanning mode at various speeds, with resolving power () ranging from 500-1500. The data were processed using SWS Interactive Analysis (de Graauw et al. 1996); IA³ using calibration files and procedures equivalent with pipeline version 7.0. Further data processing consisted of bad data removal, rebinning with a constant resolution and splicing the subbands to form a continuous spectrum. The amount of shifting between subbands is within the calibration uncertainties for the region of interest. The shifting mostly influences the strength of the emission plateaus, but has little influence on the shape.

Table 1. Log of ISO observations

In some cases, even after bad data removal, the spectra still suffer from noise due to glitches. The features discussed here are present in all available scans.

We only consider spectra with an emission plateau which satisfies the following conditions:

1. The emission plateau has to be detectable in both up and down scan.

2. The change in slope has to occur within one subband, not at the bandedges.

3. The slope in overlapping parts of the different subbands has to be the same.

4. The shifting of the subbands required to form a continous spectrum has to be within the calibration uncertainties.

© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000
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