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A search for 4750- and 4765-MHz OH masers in southern star-forming regions


Dodson, R and Ellingsen, SP, A search for 4750- and 4765-MHz OH masers in southern star-forming regions, Monthly Notices of the Royal Astronomical Society, 333, (2) pp. 307-317. ISSN 0035-8711 (2002) [Refereed Article]

DOI: doi:10.1046/j.1365-8711.2002.05428.x


We have used the Australia Telescope Compact Array (ATCA) to make a sensitive (5σ ≃ 100 mJy) search for maser emission from the 4765-MHz 2Π1/2 F = 1 → 0 transition of OH. 55 star formation regions were searched and maser emission with a peak flux density in excess of 100 mJy was detected toward 14 sites, with 10 of these being new discoveries. In addition we observed the 4750-MHz 2Π1/2 F = 1 → 1 transition towards a sample of star formation regions known to contain 1720-MHz OH masers, detecting marginal maser emission from G348.550-0.979. If confirmed this would be only the second maser discovered from this transition. The occurrence of 4765-MHz OH maser emission accompanying 1720-MHz OH masers in a small number of well-studied star formation regions has led to a general perception in the literature that the two transitions favour similar physical conditions. Our search has found that the presence of the excited-state 6035-MHz OH transition is a much better predictor of 4765-MHz OH maser emission from the same region than 1720-MHz OH maser emission is. Combining our results with those of previous high-resolution observations of other OH transitions we have examined the published theoretical models of OH masers and find that none of them predicts any conditions in which the 1665-, 6035- and 4765-MHz transitions are inverted simultaneously.

Item Details

Item Type:Refereed Article
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Dodson, R (Mr Richard Dodson)
UTAS Author:Ellingsen, SP (Professor Simon Ellingsen)
ID Code:23930
Year Published:2002
Web of Science® Times Cited:20
Deposited By:Physics
Deposited On:2002-08-01
Last Modified:2003-05-07

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