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Pre-perihelion Near-infrared high-dispersion Spectroscopy of Comet C/2013 R1 (Lovejoy) with Keck2/NIRSPEC

Presentation #322.06 in the session Comets (Poster + Lightning Talk)

Published onOct 23, 2023
Pre-perihelion Near-infrared high-dispersion Spectroscopy of Comet C/2013 R1 (Lovejoy) with Keck2/NIRSPEC

Chemical compositions of comets provide valuable clues of the chemical and physical processes that occurred in the early solar system. High-dispersion spectroscopy, especially in the near-infrared region, allows for the direct detection of various types of species (such as H2O, CO, hydrocarbons, and N-bearing species) released from the cometary nucleus, known as parent species. Comet C/2013 R1 (Lovejoy) was discovered on September 7, 2013, and it became a bright comet (approximately 5th magnitude in V-band) during its pre-perihelion passage on December 22.7, 2013, in the northern hemisphere. Based on its orbital elements (e~0.998, aorg=339.3 au, i=64.06 deg), Comet C/2013 R1 is classified as a nearly isotropic comet from the Oort cloud, making it less thermally-altered since formation compared to short-period comets that have had many close passages to the Sun. We conducted high-dispersion near-infrared spectroscopic observations of C/2013 R1 using Keck2/NIRSPEC on October 28, 2013. The heliocentric distance, geocentric distance, and relative velocity to the earth of comet C/2013 R1 was ~1.29 au, 0.70 au, and -37.33 km/s, respectively at the time of our observations. We employed two spectral settings (KL2 and KL4) to cover H2O and other minor species (HCN, NH3, C2H2, CH4, C2H6, CH3OH, H2CO). The acquired data were analyzed using IRAF, the Planetary Spectrum Generator, and our fluorescence emission model. Our results indicate that the composition of comet C/2013 R1 has typical abundances of minor species with respect to H2O compared to other comets, with the exception of C2H2 and NH3, which are significantly depleted. We will compare with other observational results and discuss the temporal variations in the composition of comet C/2013 R1.

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