New maser lines of methanol

It is found that the 4(-1)-3(0) E line (36.169 GHz) of methanol (CH3OH) is a maser in Sgr B2, with an antenna temperature of up to 60 K and a velocity width of 10 km/s. This maser is spatially extended with angular size of up to 90 arcsec, is distributed along the edge of H II regions, and apparently is not directly attached to star forming regions. Components with a narrow velocity width also exist. They are unresolved by our beam and have a velocity width of less than 1.5 km/s. We also discovered a new maser line of CH3OH, the 7(0)-6(1) A line (44.069 GHz) in Sgr B2, W51, and two other galactic sources. These two maser lines have different radial velocities. Excitation study shows that these two lines can be inverted easily but require a kinetic temperature of greater than 80 K and a fractional abundance of methanol to molecular hydrogen of 10 to the -7th for intense maser action.