The Orion-KL super water maser

Abstract

The most powerful water maser feature ever seen in Orion was monitored for seven years. The maser reached a peak flux density of about 6.7 x 10 to the 6th Jy. The total radiated energy between August 1979 and June 1987 was 6 x 10 to the 39th ergs. Three flares occurred during the period February 1980 to June 1987 superposed on a 'quiescent' flux density level of about 500,000 Jy. The maser radiation was highly linearly polarized, with the degree of polarization ranging from 45 to 65 percent. The line width and center velocity of the super maser feature varied gradually with time, changing by about 20 percent and 0.2 km/s, respectively, on time scales of about one year. If the emission arose from a saturated spherical maser cloud, the observed maser radiation parameters imply molecular hydrogen densities of about 10 to the 9th to 10 to the 11th per cu cm for pump efficiencies in the range 0.1-10 percent.