The masers towards IRAS 20126 + 4104

¹ Astronomy Dept., Faculty of science, Al-Azhar University, Naser City, Cairo, Egypt
² School of Physics and Astronomy, University of Manchester, PO Box 88, Manchester, M60 1QD, UK e-mail: G.Fuller@manchester.ac.uk
³ University of Manchester, Jodrell Bank Observatory, Macclesfield, Cheshire SK11 9DL, UK

Received: 20 August 2004
Accepted: 22 December 2004

Abstract

We present MERLIN observations of OH, water and methanol masers towards the young high mass stellar object IRAS 20126+4104. Emission from the 1665-MHz OH, 22-GHz H₂O and 6.7-GHz CH₃OH masers is detected and all originates very close to the central source. The OH and methanol masers appear to trace part of a circumstellar disk around the central source. The positions and velocities of the OH and CH₃OH masers are consistent with Keplerian rotation around a central mass of ~5 . The water masers are offset from the OH and CH₃OH masers and have significantly changed since they were last observed, but still appear to be associated to the outflow from the source. All the OH masers components are circularly polarised, in some cases reaching 100 percent while some OH components also have linear polarisation. We identify one Zeeman pair of OH masers and the splitting of this pair indicates a magnetic field of strength ~11 mG within ~ (850 AU) of the central source. The OH and CH₃OH maser emission suggest that the disk material is dense,  cm^-3, and warm,  K and the high abundance of CH₃OH required by the maser emission is consistent with the evaporation of the mantles on dust grains in the disk as a result of heating or shocking of the disk material.