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 H 2 O and 6.7-GHz CH 3 OH 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 CH 3 OH masers are consistent with Keplerian rotation around a central mass of ∼5 M . The water masers are offset from the OH and CH 3 OH 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 ∼0.5 (850 AU) of the central source. The OH and CH 3 OH maser emission suggest that the disk material is dense, n > 10 6 cm −3 , and warm, T > 125 K and the high abundance of CH 3 OH 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.

Context. Masers are important tracers of the early evolution of young high mass stars, but the relationship between different types of maser and the evolutionary state of the exciting source remains unclear. Aims. To determine whether OH masers are common towards candidate high mass protostellar objects. Methods. We present a survey of OH maser emission towards a sample of high mass protostellar objects made using the Nançay and GBT telescopes. Results. OH maser emission was detected towards 63 objects with 36 new detections. There are 56 star-forming regions and 7 OH/IR candidates. Nearly half of the detected sources have OH flux densities < ∼ 1 Jy. There is no evidence that sources with OH masers have a different range of luminosities from the non-maser sources. The results of this survey are compared with previous H 2 O and class II CH 3 OH maser observations of the same objects. Some of the detected sources are only associated with OH masers and some sources are only associated with the 1720 MHz OH maser line. The velocity range of the maser emission suggests that the water maser sources may be divided into two groups. The detection rates and velocity range of the OH and Class II CH 3 OH masers support the idea that there is a spatial association of the OH and Class II CH 3 OH masers. The sources span a wide range in R, the ratio of the methanol maser peak flux to OH 1665 MHz maser peak flux, however there are only a few sources with intermediate values of R, 8 < R < 32, which has characterised previous samples. The majority of the sources are either methanol-favoured or OH-favoured. Sources which have masers of any species, OH, water or methanol, have redder [100 µm-12 µm] IRAS colours than those without masers. However, there is no evidence for different maser species tracing different stages in the evolution of these young high mass sources. Conclusions. The detection of OH masers towards 26% of a sample of 217 sources should remove any doubt about the existence of OH maser emission towards these objects or this early evolutionary stage. Previous observations which have shown that the OH maser emission from similar sources traces the circumstellar disks around the objects. This combined with the sensitivity of the OH emission to the magnetic field, make the newly detected sources interesting candidates for future follow-up at high angular resolution.

Context. Maser emission is a strong tool for studying high mass star forming regions and their evolutionary stages. OH masers in particular can trace the circumstellar material around protostars and determine their magnetic field strengths at milliarcsecond resolution. Aims. Imaging OH maser mission towards high mass protostellar objects to determine their evolutionary stages and to locate the detected maser emission in the process of high mass star formation. Methods. In 2007, we surveyed OH maser towards 217 high mass protostellar objects to study its presence. In this paper, we present a follow up MERLIN observations of a ground state OH maser emission towards one of these objects, IRAS 19092+0841. Results. Emission from the two OH main spectral lines, 1665 and 1667 MHz, were detected close to the central object. The positions and velocities of the OH maser features have been determined. The masers are distributed over a region of ∼ 5 corresponding to 22400 AU (or ∼ 0.1 pc) at a distance of 4.48 kpc. The polarization properties of the OH maser features were determined as well. We identify three Zeeman pairs from which we inferred a magnetic field strength of ∼ 4.4mG pointing towards the observer. Conclusions. The relatively small velocity spread and the relatively wide spacial distribution of the OH maser features support the suggestion that this object could be in an early evolutionary state before the presence of disk and/or jet/outfows.