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Astron. Astrophys. 335, 1070-1076 (1998)

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A search for (H2O)2 in the Galaxy and toward comet Hale-Bopp

M. Scherer 1, M. Havenith 1, R. Mauersberger 2 and T.L. Wilson 3, 4

1 Institut für Angewandte Physik der Universität Bonn, Wegelerstr. 8, D-53115 Bonn, Germany
2 Steward Observatory, The University of Arizona, Tucson, AZ 85721, USA
3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn, Germany
4 Submillimeter Telescope Observatory, The University of Arizona, Tucson, AZ 85721, USA

Received 3 February 1998 / Accepted 21 April 1998

Abstract

The MPIfR 100 m telescope, the NRAO 12 m telescope, and the IRAM 30 m telescope were used to search for low lying rotational transitions of the water dimer, (H2O)2, toward the Galactic cloud cores Orion-KL, W51 d, W51e1e2, NGC 7538, Sgr B2(M) and L134N, and toward comet Hale-Bopp. The comet was observed on December 20, 1996 and March 25/26, 1997 (i.e. near perihelion on April 1) at 24 GHz. No lines of (H2O)2 were found. Our limit for the abundance of (H2O)2 relative to that of water (from H[FORMULA]O data) is typically [FORMULA] toward dense cloud cores. Toward Orion-KL an even more stringent limit of [FORMULA]8 10-6 is derived. The abundance of (H2O)2 relative to H2 is typically [FORMULA]. Our data show that at perihelion the production rate of the water dimer of comet C/1995 O1 (Hale-Bopp) was [FORMULA]. This is less than 6% the production rate of H2O.

Key words: ISM: abundances – ISM: molecules – radio lines: ISM – line: identification – molecular processes – comets: individual: C/1995 O1 (Hale-Bopp)

Send offprint requests to: M. Havenith

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© European Southern Observatory (ESO) 1998

Online publication: June 26, 1998
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