OH and H2O masers towards the star-forming region S140-IRS1

Abstract

Multi-Element Radio-Linked Interferometer Network polarization measurements of the OH 1.7-and 6.0-GHz, and the H2O 22-GHz masers in the massive star-forming region S140-IRS1 are presented. The observations were taken with astrometric accuracy of 15-30 mas. OH maser emission has been detected only in the ground-state 1665-MHz line. The OH masers are located approximately 2.5 arcsec north-west of IRS1. They lie in two distinct regions separated by approximately 1 arcsec along a north-east/south-west axis. Analysis of the OH maser polarization yields a magnetic field of |B| = 5.2-6.9 mG, directed towards us. The polarization position angles attest to a magnetic field which is preferentially orientated along the direction of the CO outflow associated with IRS1. The brightest H2O masers coincide in position with IRS1 and show a gradient of increasing Doppler velocity from north-west to south-east. These water masers also have proper motions of ~18 km s-1 in a similar direction. The closest OH and H2O masers are separated by more than 2 arcsec. H2O masers have also been detected at several locations up to≈0.5 arcmin distance, wheremasers have not previously been reported. The relationships between our maser observations, the central engine/object of IRS1 and the multiple outflows detected by observations at other wavelengths are also discussed. © 2010 The Authors. Journal compilation. © 2010 RAS.