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Ground-Based Infrared Detections of CO in the Centaur-comet 29P/Schwassmann-Wachmann 1 at 6.26 AU from the Sun

Paganini, Lucas and Mumma, Michael J. and Boehnhardt, Hermann and DiSanti, Michael A. and Villanueva, Geronimo L. and Bonev, Boncho P. and Lippi, Manuela and Käufl, Hans U. and Blake, Geoffrey A. (2013) Ground-Based Infrared Detections of CO in the Centaur-comet 29P/Schwassmann-Wachmann 1 at 6.26 AU from the Sun. Astrophysical Journal, 766 (2). Art. No. 100. ISSN 0004-637X. doi:10.1088/0004-637X/766/2/100.

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We observed Comet 29P/Schwassmann-Wachmann 1 (hereafter, 29P) in 2012 February and May with CRIRES/VLT and NIRSPEC/Keck-II, when the comet was at 6.26 AU from the Sun and about 5.50 AU from Earth. With CRIRES, we detected five CO emission lines on several nights in each epoch, confirming the ubiquitous content and release of carbon monoxide from the nucleus. This is the first simultaneous detection of multiple lines from any (neutral) gaseous species in comet 29P at infrared wavelengths. It is also the first extraction of a rotational temperature based on the intensities of simultaneously measured spectral lines in 29P, and the retrieved rotational temperature is the lowest obtained in our infrared survey to date. We present the retrieved production rates (~3 × 10^(28) molecules s^(–1)) and remarkably low (~5 K) rotational temperatures for CO, and compare them with results from previous observations at radio wavelengths. Along with CO, we pursued detections of other volatiles, namely H_2O, C_2H_6, C_2H_2, CH_4, HCN, NH_3, and CH_3OH. Although they were not detected, we present sensitive upper limits. These results establish a new record for detections by infrared spectroscopy of parent volatiles in comets at large heliocentric distances. Until now considered to be a somewhat impossible task with IR ground-based facilities, these discoveries demonstrate new opportunities for targeting volatile species in distant comets.

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Blake, Geoffrey A.0000-0003-0787-1610
Additional Information:© 2013 American Astronomical Society. Received 2012 November 9; accepted 2013 February 4; published 2013 March 14. Based on observations obtained at the European Southern Observatory at Cerro Paranal, Chile, under programs 088.C-0092 and 289.C-5014; and the Keck Observatory on Mauna Kea, Hawaii, under program C252ANS. We thank the VLT science operations team of the European Southern Observatory and the W. M. Keck Observatory for efficient operations of the observatories. L.P. acknowledges Retha Pretorius, Jonathan Smoker and Carla Aubel for their great assistance, and thanks Michael A’Hearn and Martin Cordiner for helpful discussions. We are also grateful to Zhong-Yi Lin and Josep Trigo-Rodríguez for providing magnitude estimations, and to the anonymous referee for helpful comments. This work was supported by NASA’s Postdoctoral (L.P.), Planetary Astronomy (PI: M.J.M. and PI: M.A.D.), and Astrobiology Programs (PI: M.J.M.), NSF (PI: B.P.B.), the Max-Planck-Gesellschaft (H.B.), and the German–Israeli Foundation for Scientific Research and Development (H.B. and M.L.).
Group:UNSPECIFIED, Division of Geological and Planetary Sciences
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Max Planck-GesellschaftUNSPECIFIED
German Israeli Foundation for Scientific Research and DevelopmentUNSPECIFIED
Subject Keywords:astrochemistry; comets: general; comets: individual (29P/Schwassmann-Wachmann 1); Kuiper belt: general; molecular processes; planets and satellites: formation
Issue or Number:2
Record Number:CaltechAUTHORS:20130503-095659127
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Official Citation:Ground-Based Infrared Detections of CO in the Centaur-comet 29P/Schwassmann-Wachmann 1 at 6.26 AU from the Sun Lucas Paganini et al. 2013 ApJ 766 100
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38258
Deposited By: Ruth Sustaita
Deposited On:03 May 2013 17:20
Last Modified:09 Nov 2021 23:36

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