Volume 521, October 2010
Herschel/HIFI: first science highlights
|Number of page(s)||5|
|Published online||01 October 2010|
Letter to the Editor
Max-Planck-Institut für Sonnensystemforschung, 37191
Katlenburg-Lindau, Germany e-mail: email@example.com
2 LESIA, Observatoire de Paris, 5 place Jules Janssen, 92195 Meudon, France
3 California Institute of Technology, Pasadena, CA 91125, USA
4 Space Research Centre, Polish Academy of Sciences, Warsaw, Poland
5 DLR, German Aerospace Centre, Bonn-Oberkassel, Germany
6 Institut d'Astrophysique et de Geophysique, Université de Liège, Belgium
7 Rosetta Science Operations Centre, European Space Astronomy Centre, European Space Agency, Spain
8 Instituto de Astrofísica de Andalucía (CSIC), Spain
9 STFC Rutherford Appleton Laboratory, Harwell Innovation Campus, Didcot, OX11 0QX, UK
10 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Belgium
11 Astronomy Department, University of Michigan, USA
12 Laboratory of Molecular Astrophysics, CAB-CSIC, INTA, Spain
13 Sterrenkundig Instituut Anton Pannekoek, University of Amsterdam, Science Park 904, 1098 Amsterdam, The Netherlands
14 LERMA, Observatoire de Paris, France
15 Joint ALMA Observatory, Chile
16 SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD, Groningen, The Netherlands
17 Leiden Observatory, University of Leiden, The Netherlands
18 Science Centre, European Space Astronomy Centre, European Space Agency, Spain
19 Department of Physics and Astronomy, University of Lethbridge, Canada
20 KOSMA, I. Physik. Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany
21 Physikalisches Institut, University of Bern, Switzerland
22 N. Copernicus Astronomical Center, Rabianska 8, 87-100, Torun, Poland
23 Istituto Fisica Spazio Interplanetario-INAF, via Fosso del Cavaliere 100, 00133 Roma, Italy
24 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Accepted: 1 July 2010
The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations of water production rates in comets. In this Letter we present HIFI observations of the fundamental 110–101 (557 GHz) ortho and 111–00 (1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and solar infrared radiation. We derive a mean water production rate of 1.0 × 1028 molecules s-1 at a heliocentric distance of 1.61 AU about 20 days before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes.
Key words: comets: individual: 81P/Wild 2 / molecular processes / radiative transfer / submillimeter: general
Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.
Figure 5 (page 5) is only available in electronic form at http://www.aanda.org
© ESO, 2010
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