Journal Article

Variability monitoring of the hydroxyl maser emission in G12.889+0.489

J. A. Green, J. L. Caswell, M. A. Voronkov and N. M. McClure-Griffiths

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 425, issue 2, pages 1504-1510
Published in print September 2012 | ISSN: 0035-8711
Published online September 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21647.x
Variability monitoring of the hydroxyl maser emission in G12.889+0.489

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Abstract

Through a series of observations with the Australia Telescope Compact Array we have monitored the variability of the ground-state hydroxyl maser emission from G12.889+0.489 in all four Stokes polarization products. These observations were motivated by the known periodicity in the associated 6.7-GHz methanol maser emission. A total of 27 epochs of observations were made over 16 months. No emission was seen from either the 1612- or 1720-MHz satellite line transitions (to a typical five sigma upper limit of 0.2 Jy). The peak flux densities of the 1665- and 1667-MHz emission were observed to vary at a level of ∼20 per cent (with the exception of one epoch which dropped by ≤40 per cent). There was no distinct flaring activity at any epoch, but there was a weak indication of periodic variability, with a period and phase of minimum emission similar to that of methanol. There is no significant variation in the polarized properties of the hydroxyl, with Stokes Q and U flux densities varying in accord with the Stokes I intensity (linear polarization, P, varying by ≤20 per cent) and the right and left circularly polarized components varying by ≤33 per cent at 1665 MHz and ≤38 per cent at 1667 MHz. These observations are the first monitoring observations of the hydroxyl maser emission from G12.889+0.489.

Keywords: masers; stars: formation

Journal Article.  3400 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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