Water in the Near IR spectrum of Comet 8P/Tuttle

TL;DR

This study presents high-resolution near-infrared spectra of Comet 8P/Tuttle, identifying new water emission lines, determining the water rotational temperature, and estimating the water production rate, thereby enhancing understanding of cometary water emission processes.

Contribution

The paper reports the first identification of new water emission lines in comet spectra, similar to 'SH' lines, and provides physical parameters like temperature and production rate.

Findings

Identified eight new H2O emission features in comet spectra.

Derived a water rotational temperature of 62 K.

Estimated water production rate as 1.4 x 10^28 molecules/sec.

Abstract

High resolution spectra of Comet 8P/Tuttle were obtained in the frequency range 3440.6-3462.6 cm-1 on 3 January 2008 UT using CGS4 with echelle grating on UKIRT. In addition to recording strong solar pumped fluorescent (SPF) lines of H2O, the long integration time (152 miutes on target) enabled eight weaker H2O features to be assigned, most of which had not previously been identified in cometary spectra. These transitions, which are from higher energy upper states, are similar in character to the so-called 'SH' lines recorded in the post Deep Impact spectrum of comet Tempel 1 (Barber et al., 2007). We have identified certain characteristics that these lines have in common, and which in addition to helping to define this new class of cometary line, give some clues to the physical processes involved in their production. Finally, we derive an H2O rotational temperature of 62+/- K and a water production rate of (1.4+/-0.3)E28 molecules/s.