Journal
ASTRONOMY & ASTROPHYSICS
Volume 521, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201015161
Keywords
comets: individual: 81P/Wild 2; molecular processes; radiative transfer; submillimeter: general
Categories
Funding
- NASA through JPL/Caltech
- NSF [AST-0540882]
- Polish Ministry of Education and Science (MNiSW)
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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 1(10)-1(01) (557 GHz) ortho and 1(11)-0(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 x 10(28) 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.
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