Journal Article

OH and H<sub>2</sub>O masers towards the star-forming region S140-IRS1

K. Asanok, S. Etoka, M. D. Gray, P. Thomasson, A. M. S. Richards and B. Hutawarakorn Kramer

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 404, issue 1, pages 120-133
Published in print May 2010 | ISSN: 0035-8711
Published online April 2010 | e-ISSN: 1365-2966 | DOI:
OH and H2O masers towards the star-forming region S140-IRS1

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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, where masers 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.

Keywords: magnetic fields; masers; polarization; stars: formation; ISM: individual: S140-IRS1

Journal Article.  8983 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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