FAR-INFRARED HYDROGEN LASERS IN THE PECULIAR STAR MWC 349A

Far-infrared hydrogen recombination lines H15 alpha (169.4 micrometers ), H12 alpha (88.8 micrometers), and H10 alpha (52.5 micrometers) were detected in the peculiar luminous star MWC 349A from the Kuiper Airbo rne Observatory. Here it is shown that at least H15 alpha is strongly amplified, with the probable amplification factor being greater than o r about equal to 10(3) and a brightness temperature that is greater th an or about equal to 10(7) kelvin. The other two lines also show signs of amplification, although to a lesser degree. Beyond H10 alpha the a mplification apparently vanishes. The newly detected amplified lines f all into the laser wavelength domain. These lasers, as well as the pre viously detected hydrogen masers, may originate in the photoionized ci rcumstellar disk of MWC 349A and constrain the disk's physics and stru cture.