Infrared Observations of Methanol in Comet P/Swift-Tuttle

Abstract

We present infrared spectroscopic observations of Comet P/Swift-Tuttle obtained with the Cryogenic Spectrometer at Kitt Peak on 1992 November 8, 9, and 12 and December 8 and 10. The spectra cover the 2.9-3.6-μm region. We detect emission from the v3 band of cometary methanol at 3.52 μm in all of our spectra. During this time, the production rate of methanol was QCH3OH = 2-6 × 1028 sec-1, with weak evidence for short-term temporal variability in QCH3OH. We find the weighted average for the relative abundance of methanol with respect to water to be 7 ± 1%, which supports the notion that methanol constitutes a significant fraction of the volatile carbon in comets. Our spectra of Comet P/Swift-Tuttle indicate that the v2 and v9 bands of methanol comprise approximately 60% of the "cometary organic feature" centered near 3.4 μm. Formaldehyde was not detected in these spectra; upper limits are presented.