Journal Article

A ‘water spout’ maser jet in S235AB-MIR

R. A. Burns, H. Imai, T. Handa, T. Omodaka, A. Nakagawa, T. Nagayama and Y. Ueno

in Monthly Notices of the Royal Astronomical Society

Volume 453, issue 3, pages 3163-3173
ISSN: 0035-8711
Published online September 2015 | e-ISSN: 1365-2966 | DOI:
A ‘water spout’ maser jet in S235AB-MIR

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We report on annual parallax and proper motion observations of H2O masers in S235AB-MIR, which is a massive young stellar object in the Perseus Arm. Using multi-epoch VLBI (very long baseline interferometry) astrometry we measured a parallax of π = 0.63 ± 0.03 mas, corresponding to a trigonometric distance of [math] kpc, and source proper motion of (μαcos δ, μδ) = (0.79 ± 0.12, −2.41 ± 0.14) mas yr−1. Water masers trace a jet of diameter 15 au which exhibits a definite radial velocity gradient perpendicular to its axis. 3D maser kinematics were well modelled by a rotating cylinder with physical parameters: vout = 45 ± 2 km s−1, vrot = 22 ± 3 km s−1, i = 12° ± 2°, which are the outflow velocity, tangential rotation velocity and line-of-sight inclination, respectively. One maser feature exhibited steady acceleration which may be related to the jet rotation. During our 15-month VLBI programme there were three ‘maser burst’ events caught ‘in the act’ which were caused by the overlapping of masers along the line of sight.

Keywords: Masers; stars: individual: S235AB-MIR; ISM: jets and outflows

Journal Article.  8330 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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