Identifying Zeeman pairs of hydroxyl masers in NGC 6334I-MM3 via velocity drift

A new tool to identify possible Zeeman pairs is presented here: the right circularly polarized (RCP) and left circularly polarized (LCP) components of a pair with velocity drift at the same rate. Long-term monitoring of hydroxyl transitions towards NGC 6334I-MM3 has resulted in the identification of three possible Zeeman pairs, one each at the 1.667, 6.030, and 6.035 GHz transitions, where the rate of drift of the RCP feature equals that of the LCP component. Historical observations suggest that their drift has been occurring over 40 yr. A fourth pair in the 1.720 GHz OH transition may indicate magnetic field variation over 50 yr.