The following document lists the file abstract/CTHUM_HIGH_RES.abs
from catalogue VI/111.
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==> In this proposal, more time is being requested for CTHUM.RRLMASER and CTHUM.DISKWIND ===================================================================== We have obtained and analysed grating scans of the full ISO wavelength range from the hydrogen recombination line maser source MWC349. Among the numerous emission lines detected we find all 12 recombination alpha lines lying in the ISO bands. They permit for the first time a virtually complete characterization of the H-maser phenomenon. The alpha lines from quantum numbers n=7 (wavelength 19 microns) up to n=15 (169 microns) are amplified, with gain increasing with wavelength. MWC349 is therefore the highest frequency celestial maser known. Here we propose to deepen our understanding of this prototypical source by obtaining with ISO velocity-resolved spectroscopy of a few selected H-recombination lines and of a few strong forbidden lines. We also wish to confirm our marginal detection of hot molecular gas in the circumstellar disk. For this work, we selected four H-lines near n=7, the onset of the maser. We expect their profiles to change systematically across the maser onset. Firstly, such changes constitute added support of maser amplification, and secondly contain information on the mechanism that quenches the maser at low n. Our hypothesis suggested by the low resolution data, namely that at low n inversion is reversed by trapped line photons, can be checked in this way. From the profiles of forbidden lines which are emitted in the ionized wind we obtain information on the wind's velocity law. The extreme range in excitation potentials of the selected lines is only excessible with ISO, and it permits us to probe the wind from near the disk, its putative origin, to well into the range of terminal velocity flow. Finally, we wish to confirm the presence of high temperature CO and H2O, the only spectroscopic evidence of neutral disk matter obtained in our preliminary analysis of the ISO grating scans by improving the signal/noise and the baseline quality in the 4.7 and 6.3 microns bands. These observations have the potential of measuring the mass and temperature of the disk for the first time.