Astron. Astrophys. 339, 159-164 (1998)

2. Observations and results

Observations have been carried out with the Short Wavelength Spectrometer (SWS) (de Graauw et al. 1996) on-board the Infrared Space Observatory satellite (Kessler et al. 1996). AOT01 full grating scan observations at speed 2 (wavelengths 2.345 µm, resolution 250) were obtained towards CoD 11721 (16h 55m 33.8s 37' 37", B1950) and MWC1080 (23h 15m 14.6s 34' 19", B1950) during revolutions 84 and 263 respectively. Raw data were processed using standard ISO-SWS reduction procedures (pipeline version 5.1). The additional analysis consisted of removing the spurious signals due to cosmic ray impacts, rescaling the detector scans to each other to reduce the noise due to uncertainties in the flux calibration and rebinning the data at twice the instrumental resolution. The above analysis has been separately carried out for the two different scan directions and the two final spectra were averaged.

Fig. 1 shows the continuum subtracted part of spectra in which the HI lines have been identified, while Table 1 lists the measured line fluxes. The uncertainty due to the flux calibration is about 30 (Schaeidt et al. 1996) and the FWHM is compatible with the nominal resolution as the lines are not spectrally resolved. The spectrum of CoD 11721 is strongly dominated by broad features of PAHs, which often make it impossible to detect lines otherwise expected to be strong, like the Pf at 3.297 µm.

Fig. 1a and b. The continuum subtracted spectra and line identifications in the wavelength ranges in which HI lines were detected (Fig. 1a for CoD 11721 and Fig. 1b for MWC1080).

Table 1. Observed line fluxes in CoD 1172 and MWC1080. For lines with S/N3 3 upper limits are considered.

© European Southern Observatory (ESO) 1998

Online publication: September 30, 1998
helpdesk.link@springer.de