Long-term monitoring of 6.7-GHz methanol masers

A sample of 54 6.7-GHz methanol masers was monitored using the Hartebeesthoek 26-m telescope during the period 1999 January – 2003 March. The observations were taken at 1–2 week intervals, with daily observations when possible if a source was seen to be varying rapidly. It was found that the majorit...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2004-12, Vol.355 (2), p.553-584
Main Authors: Goedhart, S., Gaylard, M. J., Van Der Walt, D. J.
Format: Article
Language:English
Subjects:
H ii regions
ISM: clouds
masers
radio lines: ISM
stars: formation
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Summary:A sample of 54 6.7-GHz methanol masers was monitored using the Hartebeesthoek 26-m telescope during the period 1999 January – 2003 March. The observations were taken at 1–2 week intervals, with daily observations when possible if a source was seen to be varying rapidly. It was found that the majority of the sources display a significant level of variability. The time-range of variations range from a few days up to several years. The types of behaviour observed included non-varying, monotonic increases or decreases, as well as aperiodic, quasi-periodic and periodic variations. Seven sources show clear evidence of periodicity, with periods ranging from 132 d up to 520 d.
ISSN:0035-8711
1365-2966
DOI:10.1111/j.1365-2966.2004.08340.x