Detection of three new methanol maser transitions toward star-forming regions

By using the Haystack 37 m antenna, a discovery was made of maser emission in the 7(-2)-8(-1)E, 6(2)-5(3)A(-), and 6(2)-5(3)A(+) transitions of interstellar methanol. All three lines were detected toward the compact H II regions W3(OH) and NGC 6334-F. Toward the latter source intensities in excess of 100 Jy are observed in all three transitions. Masers in the 7(-2)-8(-1)E line were detected in three additional sources. All sources toward which maser action was found are associated with compact H II regions and are known to show strong maser emission in the 12.2 GHz 2(0)-3(-1)E line of methanol at similar velocities. For this reason the newly detected masers are classified as class B methanol masers. Toward Orion-KL, thermal emission is observed.