A study of the distant activity of comet C/2006 W3 (Christensen) with Herschel and ground-based radio telescopes

Comet C/2006 W3 (Christensen) was observed in November 2009 at 3.3 AU from the Sun with Herschel.The PACS instrument acquired images of the dust coma in 70-μm and 160-μm filters and spectra covering several H_2O rotational lines. Spectra in the range 450–1550 GHz were acquired with SPIRE. The comet emission continuum from 70 to 672 μm was measured, but no lines were detected. The spectral energy distribution indicates thermal emission from large particles and provides a measure of the size distribution index and dust production rate. The upper limit to the water production rate is compared to the production rates of other species (CO, CH_3OH, HCN, H_2S, OH) measured with the IRAM 30-m and Nancay telescopes. The coma is found to be strongly enriched in species more volatile than water, in comparison to comets observed closer to the Sun. The CO to H_2O production rate ratio exceeds 220%. The dust-to-gas production rate ratio is on the order of 1.

[1]  S. Ott,et al.  Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy , 2010, 1005.5331.

[2]  S. J. Liu,et al.  Herschel : the first science highlights Special feature L etter to the E ditor The Herschel-SPIRE instrument and its in-flight performance , 2010 .

[3]  H. Roussel,et al.  In-flight calibration of the Herschel-SPIRE instrument , 2010, 1005.5073.

[4]  Miguel de Val-Borro,et al.  HIFI observations of water in the atmosphere of comet C/2008 Q3 (Garradd) , 2010, 1005.2969.

[5]  L. Colangeli,et al.  A survey on the distant activity of short period comets , 2009 .

[6]  Nicolas Thomas,et al.  Water and Related Chemistry in the Solar System. A Guaranteed Time Key Programme for Herschel , 2009 .

[7]  Thomas Henning,et al.  The Photodetector Array Camera and Spectrometer (PACS) for the Herschel Space Observatory , 2004, Astronomical Telescopes + Instrumentation.

[8]  Submillimetre observations of comets with Odin: 2001 - 2005 , 2006, astro-ph/0610779.

[9]  V. Zakharov,et al.  Direct Monte Carlo and multifluid modeling of the circumnuclear dust coma , 2005 .

[10]  Edwin A. Bergin,et al.  The Pure Rotational Line Emission of Ortho-Water Vapor in Comets. I. Radiative Transfer Model , 2004 .

[11]  N. Thomas,et al.  Long-term optical spectrophotometric monitoring of comet C/1995 O1 (Hale-Bopp) , 2003 .

[12]  G. Bourgois,et al.  Observations at Nançay of the OH 18-cm lines in comets - The data base. Observations made from 1982 to 1999 , 2002 .

[13]  A. Winnberg,et al.  The 1995-2002 Long-Term Monitoring of Comet C/1995 O1 (HALE-BOPP) at Radio Wavelength , 2002 .

[14]  R. Moreno,et al.  Spectroscopic Monitoring of Comet C/1996 B2 (Hyakutake) with the JCMT and IRAM Radio Telescopes , 1999 .

[15]  J. Crifo,et al.  The Dependence of the Circumnuclear Coma Structure on the Properties of the Nucleus , 1997 .

[16]  D. Jewitt,et al.  The submillimeter radio continuum of Comet P/Brorsen-Metcalf , 1990 .