2005/07/02 by M. A. Voronkov, Alexandre N. Sobolev, A. M. Sobolev +2 · 34 citations
Chemistry · Earth and Planetary Sciences · Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Atmospheric Ozone and Climate #Atomic physics #Brightness #Brightness temperature #Excited state #Maser #Meteorology #Methanol #Molecular Spectroscopy and Structure #Orion Nebula #Outflow #Physics #Radio telescope #Stars #Telescope #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2005.09374.x
published in Monthly Notices of the Royal Astronomical Society 362(3), 995-1005 (Oxford University Press) · 11 pages, 5 figures, 4 tables, mn2e.cls included; accepted by MNRAS
arxiv created 2005/07/02 · openalex publication_date 2005/09/02 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The Australia Telescope Compact Array (ATCA) has been used to search for methanol maser emission at 6.7 GHz towards the Orion Molecular Cloud 1 (OMC-1). Two features peaking at 7.2 and −1.1 km s−1 have been detected. The former has at least two components close in both velocity and position. It is located south-east of the Orion Kleinmann-Low (Orion-KL) nebula in the region of outflow traced by the 25-GHz methanol masers and the 95-GHz methanol emission. It is shown by modelling that, in contrast to the widespread opinion that simultaneous masing of methanol transitions of different classes is impossible, there are conditions for which simultaneous masing of the class II transition at 6.7 GHz and some class I transitions (e.g. the series at 25 GHz) is possible. A relevant example is provided, in which the pumping occurs via the first torsionally excited state and is driven by radiation of the dust intermixed with the gas in the cloud. In this regime, the dust temperature is significantly lower (T≈ 60 K) than in the case of bright 6.7-GHz masers (T > 150 K). The narrow spectral feature at −1.1 km s−1 has a brightness temperature greater than about 1400 K, which suggests that it is probably a maser. It emanates from the Orion South region and is probably associated with the approaching part of outflow seen in CO. The 25-GHz maser associated with OMC-1 was observed quasi-simultaneously with the 6.7-GHz observations. No 25-GHz emission associated with the −1.1 km s−1 6.7-GHz feature towards Orion South was detected.