GBT24A-429

Monitoring MonR2 maser polarization during a flaring event

Abstract

The 4.765 GHz excited OH maser in MonR2 is the only example of this maser line to have exhibited linear polarisation. This maser has been observed to flare at irregular intervals, with the physical mechanism producing the flaring and the polarization not yet determined.
This source was observed as part of project GBT22B-354 (full Stokes measurements of excited OH masers) and was seen in July 2023 to be flaring (intensity about 27 Jy) after a quiescent period which started at end 2019. Observation in December 2023 indicated a broader maser linewidth also exhibiting linear polarisation but with slightly different values.
Both July and December observations indicated circular polarisation which is not expected and has not been detected previously. In addition, during the December observation, thermal emission was observed at 4.750 GHz together with absorption at the 6.031 GHz and the 6.035 GHz main line transition frequencies - these have not been detected previously.
This request, to measure the maser once a month over the next six months, will monitor the flaring, the maser line velocity profile (should it suggest more than one maser) and the polarisation characteristics.

Investigators

Name	Institution
Paul Fallon *	South Africa, University of
Derck Smits	South Africa, University of

* indicates the PI