Hyperfine structure of the methanol molecule as traced by Class I methanol masers
In one sentence
A combined observational and theoretical campaign showing that each Class I methanol maser source amplifies one specific hyperfine component of the methanol transition — and that the dominant component changes from source to source — refining methanol’s already-impressive credentials as a precision tracer of physical conditions.
What’s the question?
Class I methanol masers are bright, narrow, and ubiquitous around regions of high-mass star formation. Each maser line is in fact a multiplet of closely-spaced hyperfine components — and which component dominates the maser emission depends on the local conditions in a non-trivial way. To use these masers for any quantitative measurement (magnetic fields, fundamental-constant tests, kinematics), we need to know exactly which hyperfine component is doing the work.
What did we do?
The team carried out high-precision Effelsberg observations of Class I methanol masers at multiple frequencies (36, 44, and 95 GHz), and combined them with quantum-chemical modelling and laboratory measurements of the methanol hyperfine spectrum. The result: refined centre frequencies of the hyperfine multiplets, evidence that one specific hyperfine transition forms each maser, and the realisation that the identity of that “favoured” transition can change from source to source. Comparison with Korean-telescope data taken 6-10 years earlier showed the maser line profiles to be kinematically stable.
Why does it matter?
Refining methanol’s hyperfine fingerprint sharpens the maser as a precision tool — for magnetic-field measurements, for tests of fundamental constants, and for tracing the dynamics of star-forming gas.
My role
Co-author. Contributed the underlying methanol hyperfine theory (from earlier work) that anchors the laboratory and astronomical interpretation.