EDP Sciences
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Volume 406, Number 2, August I 2003
Page(s) L47 - L50
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20030932

A&A 406, L47-L50 (2003)
DOI: 10.1051/0004-6361:20030932


Far-infrared detection of $^{\mathsf{17}}$OH towards Sagittarius B2

E. T. Polehampton1, J. M. Brown2, B. M. Swinyard3 and J.-P. Baluteau4

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: epoleham@mpifr-bonn.mpg.de
2  Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, UK
    e-mail: john.m.brown@chem.ox.ac.uk
3  Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK
    e-mail: B.M.Swinyard@rl.ac.uk
4  Laboratoire d'Astrophysique de Marseille, CNRS & Université de Provence, BP 8, 13376 Marseille Cedex 12, France
    e-mail: Jean-Paul.Baluteau@oamp.fr

(Received 31 January 2003 / Accepted 19 June 2003)

The frequencies and line strengths of the $^{2}\Pi_{3/2}~J=5$/2-3/2 rotational transition of  17OH have been calculated from an analysis of its far-infrared laser magnetic resonance spectrum. These results have been used to make the first detection of a pure rotational transition of  17OH in the ISM. Two resolved components of this transition appear in absorption towards the giant molecular cloud Sagittarius B2, which was observed at a spectral resolution of 33 km s -1 with the Fabry-Pérot mode of the ISO Long Wavelength Spectrometer. The corresponding transition of  18OH was also observed and its line shape was modelled using $\ion{H}{i}$ measurements. The 18O/ 17O ratio of 3.5 was then used to compare this with the observed 17OH line shape.

Key words: infrared: ISM -- molecular data -- ISM: molecules -- line: identification -- ISM: individual objects: Sagittarius B2

Offprint request: E. Polehampton, epoleham@mpifr-bonn.mpg.de

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