Astronomy and Astrophysics – Astrophysics
Scientific paper
Jun 1988
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1988a%26a...198..267m&link_type=abstract
Astronomy and Astrophysics, Vol. 198, NO. 1/2/JUN, P. 267, 1988
Astronomy and Astrophysics
Astrophysics
25
Scientific paper
We have used the 100-m telescope (HPBW =38") to observe the 25 GHz J2 → J1 (J =2 to 8) maser transitions of E-type methanol towards Orion-KL and nearby condensations in the Orion ridge. In general, the spatial distribution of the emission is similar to that observed in mm-wavelength lines where maser action is presumably not occurring. We have fit a crude excitation model to the observed dependence of maser flux upon J and find that the data are consistent with a rotation temperature of 100 K which is similar to that found for nonmasing methanol. The corresponding column density averaged over our beam is roughly 1016 cm-2 which is consistent with a methanol abundance in the maser region between 10-8 and 10-6. We have readdressed the question of time variability by mapping the region showing maser emission twice within a thirteen month interval. Our data allow at most 20% variability between February 1986 and March 1987 and are consistent with much earlier (Hills et al., 1974) Effelsberg observations. Additionally, we have detected J2 → J1, narrow band emission towards OMC2.
Henkel Carsten
Menten Karl. M.
Walmsley Charles Malcolm
Wilson Thomas L.
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