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Astron. Astrophys. 357, L37-L40 (2000)

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Letter to the Editor

Magnetic field structure of the cometary HII region G34.3+0.2

Magnetic field structure of G34.3+0.2

X. Zheng 1,2, M.J. Reid 2 and J.M.Moran 2

1 Nanjing University, Department of Astronomy, Nanjing 210093, P.R. China
2 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA

Received 23 September 1999 / Accepted 20 April 2000


We observed the hydroxyl (OH) masers in the ground-state 1665 and 1667 MHz transitions toward the cometary HII region G34.3+0.2 with the Very Long Baseline Array (VLBA). Our observations were sensitive to both right and left circular polarizations with a spectral resolution of 0.176 km s-1 and an angular resolution of [FORMULA] mas. We detected 120 maser features in a region of [FORMULA] arcsec, including 15 Zeeman pairs separated by an average distance of only 2 mas were identified. The OH masers are associated with two newly formed stars in the G34.3+0.2 complex. One star ionizes a weak, ultra-compact HII region (source B) and has a magnetic field orientation predominantly away from us. The other star, or stars, power the dominant cometary HII region (source C) and the magnetic field along the northern rim of the cometary source is directed toward us.

Key words: masers – polarization – stars: formation – ISM: individual objects: G34.3+0.2

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© European Southern Observatory (ESO) 2000

Online publication: June 5, 2000