GALACTIC METHANOL MASERS AT 12 GHZ

We have detected 12-GHz methanol maser emission from 131 of 238 6.6-GH z masers searched. The peak flux densities at 12 GHz range from 1200 t o 0.4 Jy with a median value of 7 Jy. Individual spectral features of the two transitions often coincide, although with a wide range of rela tive intensities, so that the detailed appearances of the 12- and 6.6- GHz spectra often differ considerably. Where an individual spot (or sp ectral feature) does mase at both transitions, the relative intensitie s can indicate the physical conditions in the spot. The 12-GHz feature s are typically several times weaker than their 6.6-GHz counterparts, but there are instances where they are stronger, and these most likely delineate spots of higher than average density. From many masers, in both transitions, at least a quarter of the features show significant intensity variations on a time-scale of several months, Although the q uiescent features are probably saturated, some of the more variable fe atures, especially those at 12 GHz, may not be saturated.