First detections of methanol maser lines from a rare transition family

We report the first observations in a rare family of class II methanol maser transitions in both CH 3 OH and 13 CH 3 OH toward three southern high-mass star formation regions, along with the first maser detected in the 13 CH 3 OH line. The 8 2 → 9 1 A − methanol transition was observed in both CH 3 OH and 13 CH 3 OH (at 28.9 GHz and 41.9 GHz respectively) toward three sources; G358.93-0.03, NGC6334I and G345.01+1.79, all of which are star formation regions with recent maser flaring events. We report the first maser detection of the 41.9 GHz line in 13 CH 3 OH toward G358.93-0.03 and the first confirmed maser detection of the 28.9 GHz line in CH 3 OH toward NGC6334I. Additionally we report a maser detection of the 28.9 GHz line in CH 3 OH toward G358.93-0.03, meaning that with our detection of the 41.9 GHz line, this is the first isotopic detection of these lines toward G358.93-0.03. The newly detected maser transitions are associated with the primary millimetre continuum sources (MM1) in both G358.93-0.03 and NGC6334I, within the varying positional uncertainties.