Galactic methanol masers at 12 GHz

We have detected 12-GHz methanol maser emission from 131 of 238 6.6-GHz masers searched. The peak flux densities at 12 GHz range from 1200 to 0.4 Jy with a median value of 7Jy. Individual spectral features of the two transitions often coincide, although with a wide range of relative intensities, so that the detailed appearances of the 12- and 6.6-GHz spectra often differ considerably. Where an individual spot (or spectral feature) does mase at both transitions, the relative intensities can indicate the physical conditions in the spot. The 12-GHz features 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 quiescent features are probably saturated, some of the more variable features, especially those at 12 GHz, may not be saturated.