Other
Scientific paper
Oct 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010dps....42.2815m&link_type=abstract
American Astronomical Society, DPS meeting #42, #28.15; Bulletin of the American Astronomical Society, Vol. 42, p.962
Other
Scientific paper
We present analysis of high spectral resolution observations of the forbidden oxygen lines at 5577, 6300 and 6364 angstroms in comets C/2006 W3 Christensen and C/2007 Q3 Siding Spring, acquired at approximately 3 AU from the Sun. We obtained the data using the ARCES echelle spectrometer (R=31,500) mounted on the Apache Point Observatory 3.5 meter telescope. We observed C/2006 W3 on UT August 1 2009, while C/2007 Q3 was observed on UT March 28 2010. Most published observations of these lines in other comets were obtained at small heliocentric distances (approx. 1 AU), where photodissociation of water molecules is the dominant source of the atomic oxygen present in the coma. However, at larger heliocentric distances, water sublimation drops off and molecules such as CO and CO2 may play a larger role, as suggested by the comparable production rates of CO and OH in comet C/1995 O1 Hale-Bopp at 3 AU. The relative role of H2O vs. CO/CO2 as a source of atomic oxygen can be examined by comparing the ratio of the green line (5577) to the red doublet (6300 and 6364). For C/2006 W3, we detect all three lines, and therefore the line ratio can be directly calculated. For C/2007 Q3 Siding Spring, we detect only the 6300 line, and therefore we can only place an upper limit on the value of the ratio. Since observing conditions were photometric for C/2007 Q3, we are able to perform a flux calibration of the 6300 line. We use this flux to calculate the production rate of H2O, CO, and CO2 for cases where QH2O >> QCO2, QCO2 >> QH2O, and QH2O = QCO2, assuming the number density of atomic oxygen is described by a Haser Model. This work was supported by the NASA EPSCoR program through grant number NNX08AV85A.
Chanover Nancy
Cochran Anita
Dello Russo Neil
Harris William
McKay Adam
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