A BIMA Array Survey of Molecules in Comets LINEAR (C/2002 T7) and NEAT (C/2001 Q4)

Abstract

We present an interferometric search for large molecules, including methanol (CH_3OH), methyl cyanide (CH_3CN), ethyl cyanide (CH_3CH_2CN), ethanol (CH_3CH_2OH), and methyl formate (CH_3OCHO), in comets LINEAR (C/2002 T7) and NEAT (C/2001 Q4) with the Berkeley-Illinois-Maryland Association (BIMA) array. We also searched for transitions of the simpler molecules CS, SiO, HNC, HN^(13)C, and ^(13)CO. We detected transitions of CH_3OH and CS around comet LINEAR and one transition of CH_3OH around comet NEAT within a synthesized beam of ~20". We calculated the total column density and production rate of each molecular species using the variable temperature and outflow velocity (VTOV) model recently described by Friedel et al. Considering the molecular production rate ratios with respect to water, comet T7 LINEAR is more similar to comet Hale-Bopp, while comet Q4 NEAT is more similar to comet Hyakutake. It is unclear, however, due to such a small sample size, whether there is a clear distinction between a Hale-Bopp and Hyakutake class of comet or whether comets have a continuous range of molecular production rate ratios.

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