EDP Sciences
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Volume 387, Number 1, May III 2002
Page(s) 310 - 316
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20020358

A&A 387, 310-316 (2002)
DOI: 10.1051/0004-6361:20020358

Torsionally excited methanol at 44.9 GHz

M. A. Voronkov1, M. C. Austin2, 3 and A. M. Sobolev4

1  Astro Space Center, Profsouznaya st. 84/32, 117997 Moscow, Russia
2  The Catholic University of America, 620 Michigan Ave., Washington, DC 20064, USA
3  Maria Mitchell Observatory, 59 Milk st., Nantucket, MA 02554, USA
4  Astronomical Observatory, Ural State University, Lenin st. 51, 620083 Ekaterinburg, Russia

(Received 17 July 2001 / Accepted 6 March 2002)

Using the Haystack Observatory 37-m radio telescope we have undertaken a search for emission in the 20-31 E rotational transition of methanol in its first torsionally excited state ( $v\rm _t = 1$) at 44.9 GHz. We examined seven galactic sources - six strong emitters of Class II methanol maser lines and Orion KL , the only source where this line had been previously detected. We confirm (at a level of $5\sigma$) the previous detection and report two new detections - a reliable ( $9\sigma$) detection in W3(OH) and a marginal ( $3.5\sigma$) detection in NGC 6334F . Upper limits for other sources are presented. Although we did not see obvious signatures of maser amplification in this transition in any source, arguments in favor of weak masing in W3(OH) are presented.

Key words: masers -- ISM: molecules -- ISM: individual objects: W3(OH), Orion KL, NGC 6334F -- stars: formation

Offprint request: M. A. Voronkov, voronkov@tanatos.asc.rssi.ru

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