2001A&A...371.1012S

The OH 1612MHz maser transition from the supergiant star VX Sgr has been imaged in all Stokes parameters using MERLIN. Numerous elliptically polarised components are distributed in a roughly symmetric envelope of a size similar to that measured in total maser intensity. The polarisation vectors are generally tangential to the circumstellar envelope, indicating a globally ordered magnetic field at the distance of about 1400au from the supergiant. It is suggested that a predominance of projected radial magnetic lines and a displacement between the red- and blue-shifted parts of the envelope can be explained with a dipole field tilted at 20-30° to the line of sight.