TY - JOUR
T1 - Methane in Oort cloud comets
AU - Gibb, E. L.
AU - Mumma, M. J.
AU - Dello Russo, N.
AU - DiSanti, M. A.
AU - Magee-Sauer, K.
N1 - Funding Information:
E.L. Gibb gratefully acknowledges support from the National Research Council under her Resident Research Associateship. This work was also supported by NASA Planetary Astronomy RTOP 693-344-32-30-07 to M.J. Mumma. N. Dello Russo was supported by NASA Planetary Atmospheres program grants NAG5-10795 and NAG5-12285. M.A. DiSanti was supported by NASA Planetary Astronomy program grants NAG5-7905 and NAG5-12208. K. Magee-Sauer was supported by the National Science Foundation Research at Undergraduates Institution program under grant AST-009841. We give a special thank you to H. Weaver for collaborating on WM 1 observations at the W.M. Keck Observatory. We also acknowledge vital assistance provided by staffs of the IRTF and Keck in acquiring the data. The W.M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. The NASA IRTF is operated by the University of Hawaii under contract to NASA. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
PY - 2003/10/1
Y1 - 2003/10/1
N2 - We detected CH4 in eight Oort cloud comets using high-dispersion (λ/Δ ∼ 2 × 104) infrared spectra acquired with CSHELL at NASA's IRTF and NIRSPEC at the W.M. Keck Observatory. The observed comets were C/1995 O1 (Hale-Bopp), C/1996 B2 (Hyakutake), C/1999 H1 (Lee), C/1999 T1 (McNaught-Hartley), C/1999 S4 (LINEAR), C/2000 WM1 (LINEAR), C/2001 A2 (LINEAR); and 153/P Ikeya-Zhang (C/2002 C1). We detected the R0 and R1 lines of the ν3 vibrational band of CH4 near 3.3 μm each comet, with the exception of McNaught-Hartley where only the R0 line was measured. In order to obtain production rates, a fluorescence model has been developed for this band of CH4. We report g-factors for the R0 and R1 transitions at several rotational temperatures typically found in comet comae and relevant to our observations. Using g-factors appropriate to Trot as determined from HCN, CO and/or H2O and C2H6, CH4 production rates and mixing ratios are presented. Abundances of CH4/H2O are compared among our existing sample of comets, in the context of establishing their place of origin. In addition, CH4 is compared to native CO, another hypervolatile species, and no correlation is found among the comets observed.
AB - We detected CH4 in eight Oort cloud comets using high-dispersion (λ/Δ ∼ 2 × 104) infrared spectra acquired with CSHELL at NASA's IRTF and NIRSPEC at the W.M. Keck Observatory. The observed comets were C/1995 O1 (Hale-Bopp), C/1996 B2 (Hyakutake), C/1999 H1 (Lee), C/1999 T1 (McNaught-Hartley), C/1999 S4 (LINEAR), C/2000 WM1 (LINEAR), C/2001 A2 (LINEAR); and 153/P Ikeya-Zhang (C/2002 C1). We detected the R0 and R1 lines of the ν3 vibrational band of CH4 near 3.3 μm each comet, with the exception of McNaught-Hartley where only the R0 line was measured. In order to obtain production rates, a fluorescence model has been developed for this band of CH4. We report g-factors for the R0 and R1 transitions at several rotational temperatures typically found in comet comae and relevant to our observations. Using g-factors appropriate to Trot as determined from HCN, CO and/or H2O and C2H6, CH4 production rates and mixing ratios are presented. Abundances of CH4/H2O are compared among our existing sample of comets, in the context of establishing their place of origin. In addition, CH4 is compared to native CO, another hypervolatile species, and no correlation is found among the comets observed.
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U2 - 10.1016/S0019-1035(03)00201-X
DO - 10.1016/S0019-1035(03)00201-X
M3 - Article
AN - SCOPUS:0141457123
SN - 0019-1035
VL - 165
SP - 391
EP - 406
JO - Icarus
JF - Icarus
IS - 2
ER -