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C/2013 R1 (Lovejoy) at IR Wavelengths and the Variability of CO Abundances among Oort Cloud Comets

Paganini, L. and Mumma, M. J. and Villanueva, G. L. and Keane, J. V. and Blake, G. A. and Bonev, B. P. and DiSanti, M. A. and Gibb, E. L. and Meech, K. J. (2014) C/2013 R1 (Lovejoy) at IR Wavelengths and the Variability of CO Abundances among Oort Cloud Comets. Astrophysical Journal, 791 (2). Art. No. 122. ISSN 0004-637X.

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We report production rates, rotational temperatures, and related parameters for gases in C/2013 R1 (Lovejoy) using the Near InfraRed SPECtrometer at the Keck Observatory, on six UT dates spanning heliocentric distances (R_h ) that decreased from 1.35 AU to 1.16 AU (pre-perihelion). We quantified nine gaseous species (H_2O, OH^*, CO, CH^4, HCN, C_2H_6, CH_3OH, NH_3, and NH_2) and obtained upper limits for two others (C_2H_2 and H_2CO). Compared with organics-normal comets, our results reveal highly enriched CO, (at most) slightly enriched CH_3OH, C_2H_6, and HCN, and CH_4 consistent with "normal", yet depleted, NH_3, C_2H_2, and H_2CO. Rotational temperatures increased from ~50 K to ~70 K with decreasing R_h , following a power law in R_h of –2.0 ± 0.2, while the water production rate increased from 1.0 to 3.9 × 10^(28) molecules s^(–1), following a power law in R_h of –4.7 ± 0.9. The ortho-para ratio for H_2O was 3.01 ± 0.49, corresponding to spin temperatures (T_(spin)) ≥ 29 K (at the 1σ level). The observed spatial profiles for these emissions showed complex structures, possibly tied to nucleus rotation, although the cadence of our observations limits any definitive conclusions. The retrieved CO abundance in Lovejoy is more than twice the median value for comets in our IR survey, suggesting this comet is enriched in CO. We discuss the enriched value for CO in comet C/2013 R1 in terms of the variability of CO among Oort Cloud comets.

Item Type:Article
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Blake, G. A.0000-0003-0787-1610
Meech, K. J.0000-0002-2058-5670
Additional Information:© 2014 American Astronomical Society. Received 2014 March 26; accepted 2014 June 30; published 2014 August 6. We gratefully acknowledge support by NASA’s PAST Program (L.P., M.J.M, M.A.D., G.L.V.) and NAI through its member Teams at GSFC (M.J.M., M.A.D., B.P.B., G.A.B.) and at UH (J.V.K., K.J.M.; No. NNA09DA77A), and NSF (B.P.B., E.L.G.; Award 1211362). The data of October 24 and 25 were collected during part of the NASA Keck time awarded for observations of comet ISON, and are publicly available through the Keck Observatory Archive. We thank the anonymous referee for useful insights on this paper. The authors 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.
Funding AgencyGrant Number
Subject Keywords:astrochemistry; comets: general; comets: individual (C/2013 R1 (Lovejoy)); infrared: planetary systems; molecular processes; Oort Cloud
Issue or Number:2
Record Number:CaltechAUTHORS:20140904-114820603
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Official Citation:C/2013 R1 (Lovejoy) at IR Wavelengths and the Variability of CO Abundances among Oort Cloud Comets L. Paganini et al. 2014 ApJ 791 122
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:49242
Deposited By: Ruth Sustaita
Deposited On:04 Sep 2014 19:19
Last Modified:31 Oct 2019 02:24

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