HIFI Observations of Water in the Atmosphere of Comet C/2008 Q3 (Garradd)

P. Hartogh (1) , J. Crovisier (2) , M. de Val-Borro , D. Bockelée-Morvan (2) , N. Biver (2) , D. C. Lis (3) , R. Moreno (2) , C. Jarchow , M. Rengel , M. Emprechtinger , S. Szutowicz , M. Banaszkiewicz (4) , F. Bensch , M. I. Blecka (5) , T. Cavalié (6, 7, 8, 9) , T. Encrenaz (2) , E. Jehin (10) , M. Küppers (1) , L. -M. Lara , E. Lellouch (2) , B. M. Swinyard , B. Vandenbussche , E. A. Bergin (11) , G. A. Blake (12) , J. A. D. L. Blommaert , J. Cernicharo (13) , L. Decin (14) , P. Encrenaz (15) , T. de Graauw , D. Hutsemekers , M. Kidger , J. Manfroid , A. S. Medvedev , D. A. Naylor , R. Schieder , N Thomas (16) , C. Waelkens , P. R. Roelfsema , P. Dieleman , R. Guesten , T. Klein (17) , C. Kasemann , M. Caris , M. Olberg (18) , A. O. Benz

1 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
2 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
3 CALTECH - California Institute of Technology
4 CBK - Space Research Centre of Polish Academy of Sciences
5 PAN - Polska Akademia Nauk = Polish Academy of Sciences = Académie polonaise des sciences
6 LAB - Laboratoire d'Astrophysique de Bordeaux [Pessac]
7 OASU - Observatoire aquitain des sciences de l'univers
8 UB - Université Sciences et Technologies - Bordeaux 1
9 L3AB - Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux
10 ESO - European Southern Observatory
11 CfA - Harvard-Smithsonian Center for Astrophysics
12 LOCIE - LabOratoire proCédés énergIe bâtimEnt
13 CSIC - Centro de Investigaciones Biológicas
14 Instituut voor Sterrenkunde [Leuven]
15 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
16 UNIBE - Universität Bern / University of Bern
17 MPIFR - Max-Planck-Institut für Radioastronomie
18 Onsala Space Observatory

High-resolution far-infrared and sub-millimetre spectroscopy of water lines is an important tool to understand the physical and chemical properties of cometary atmospheres. We present observations of several rotational ortho- and para-water transitions in comet C/2008 Q3 (Garradd) performed with HIFI on Herschel. These observations have provided the first detection of the 2_{12}-1_{01} (1669 GHz) ortho and 1_{11}-0_{00} (1113 GHz) para transitions of water in a cometary spectrum. In addition, the ground-state transition 1_{10}-1_{01} at 557 GHz is detected and mapped. By detecting several water lines quasi-simultaneously and mapping their emission we can constrain the excitation parameters in the coma. Synthetic line profiles are computed using excitation models which include excitation by collisions, solar infrared radiation, and radiation trapping. We obtain the gas kinetic temperature, constrain the electron density profile, and estimate the coma expansion velocity by analyzing the map and line shapes. We derive water production rates of 1.7-2.8 x 10^{28} s^{-1} over the range r_h = 1.83-1.85 AU.

Mots clés: comets: individual: C/2008 Q3; radio lines: general; submillimeter: general; techniques: spectroscopic

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]; Planétologie et astrophysique de la terre [astro-ph.EP]

P. Hartogh, J. Crovisier, M. de Val-Borro, D. Bockelée-Morvan, N. Biver, et al.. HIFI Observations of Water in the Atmosphere of Comet C/2008 Q3 (Garradd). Astronomy and Astrophysics - A&A, 2010, 518, pp.L150. ⟨10.1051/0004-6361/201014665⟩. ⟨hal-00521675⟩