2. Observations and data reduction
The observations were obtained with the Short Wavelength Spectrometer (SWS; de Graauw et al. 1996b) on board the ISO satellite (Kessler et al. 1996). A complete spectrum (2.4 to 45 µm) of NGC7538 IRS1 has been taken in grating mode AOT01 at speed 2 with an effective resolution of about 250, during revolution 91 pointing at , 1950.
The raw data were reduced using the standard ISO-SWS reduction procedure (OLP version 5.1); subsequent analysis consisted in removing spurious signals due to cosmic ray impacts and rebinning the data at the instrumental resolution. To reduce the noise due to inaccuracies in the flux calibration of the different detectors, before rebinning the detector scans were scaled to each other by fitting straight lines and multiplying each scan to the mean level.
© European Southern Observatory (ESO) 1998
Online publication: June 2, 1998