First detections of methanol maser lines from a rare transition family

Abstract

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 $8_2\to 9_1{A}^{-}$ 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.

This paper has been accepted for publication in Publications of the Astronomical Society of Australia (PASA). At the time of this submission it is available online as Open Access