Wilson, TG;
Rawlings, JMC;
Swinyard, BM;
(2017)
Herschel/SPIRE observations of water production rates and ortho-to-para ratios in comets.
Monthly Notices of the Royal Astronomical Society
, 466
(2)
pp. 1954-1962.
10.1093/mnras/stw3152.
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Abstract
This paper presents Herschel/SPIRE (Spectral and Photometric Imaging Receiver) spectroscopic observations of several fundamental rotational ortho- and para-water transitions seen in three Jupiter-family comets and one Oort-cloud comet. Radiative transfer models that include excitation by collisions with neutrals and electrons, and by solar infrared radiation, were used to produce synthetic emission line profiles originating in the cometary coma. Ortho-to-para ratios (OPRs) were determined and used to derived water production rates for all comets. Comparisons are made with the water production rates derived using an OPR of 3. The OPR of three of the comets in this study is much lower than the statistical equilibrium value of 3; however they agree with observations of comets 1P/Halley and C/2001 A2 (LINEAR), and the protoplanetary disc TW Hydrae. These results provide evidence suggesting that OPR variation is caused by post-sublimation gas-phase nuclear-spin conversion processes. The water production rates of all comets agree with previous work and, in general, decrease with increasing nucleocentric offset. This could be due to a temperature profile, additional water source or OPR variation in the comae, or model inaccuracies.
| Type: | Article |
|---|---|
| Title: | Herschel/SPIRE observations of water production rates and ortho-to-para ratios in comets |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/stw3152 |
| Publisher version: | http://dx.doi.org/10.1093/mnras/stw3152 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | molecular processes, radiative transfer, techniques: spectroscopic, comets: general, comets: individual: 103P/Hartley 2, 10P/Tempel 2, 45P/Honda-Mrkos-Pajdusakova, C/2009 P1 (Garradd), submillimetre: general, C/2009 P1 GARRADD, 103P/HARTLEY 2, RADIATIVE-TRANSFER, LYMAN-ALPHA, INNER COMA, ROTATIONAL TEMPERATURES, SOHO/SWAN OBSERVATIONS, INTERSTELLAR WATER, SWAN INSTRUMENT, 2010 APPARITION |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10042362 |
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