Detailed Analysis of Near-IR Water (H2O) Emission in Comet C/2014 Q2 (LOVEJOY) with the GIANO/TNG Spectrograph

We observed the Oort cloud comet C/2014 Q2 (Lovejoy) on 2015 January 31 and February 1 and 2 at a heliocentric distance of 1.3 au and geocentric distance of 0.8 au during its approach to the Sun. Comet Lovejoy was observed with GIANO, the near-infrared high-resolution spectrograph mounted at the Nasmyth-A focus of the TNG (Telescopio Nazionale Galileo) telescope in La Palma, Canary Islands, Spain. We detected strong emissions of radical CN and water, along with many emission features of unidentified origin, across the 1-2.5 μm region. Spectral lines from eight ro-vibrational bands of H2O were detected, six of them for the first time. We quantified the water production rate [Q(H2O), (3.11 ± 0.14) × 1029 s-1] by comparing the calibrated line fluxes with the Goddard full non-resonance cascade fluorescence model for H2O. The production rates of ortho-water [Q(H2O)ORTHO, (2.33 ± 0.11) × 1029 s-1] and para-water [Q(H2O)PARA, (0.87 ± 0.21) × 1029 s-1] provide a measure of the ortho-to-para ratio (2.70 ± 0.76)). The confidence limits are not small enough to provide a critical test of the nuclear spin temperature