Abstract
We report a weak detection of HCN J=1--0 emission from comet C/1999 S4 (LINEAR) with the Berkeley-Illinois-Maryland Association (BIMA) Array in auto-correlation mode, in the three days prior to this comet's breakup on 2000 July 25 (M. Kidger, IAUC 7467). The antenna temperature of 3.5 +/- 1.0 mK in the 130'' beam suggests an outgassing rate at a few percent of that of comet C/1995 O1 (Hale-Bopp). Cross-correlation observations during the same period with the BIMA array in tandem with the Caltech Millimeter Array at the Owens Valley Radio Observatory (OVRO) do not reveal any HCN 1--0 emission. Detailed model calculations including accurate (u,v) sampling predict a 10 σ signal for a standard Haser model at the outgassing rate derived above. The observed non-detection in cross-correlation mode suggests a more extended source size. These observations are the first to combine simultaneous data from the BIMA and OVRO arrays, known as the `virtual' Combined Array for Research in Millimeter-wave Astronomy (CARMA). M.R.H. is supported by the Miller Institute for Basic Research in Science. This work was partially funded by: NASA NAG5-4292, NAG5-4080, NAG5-8708, and NGT5-0083; NSF AST 96-13998, AST96-13999, AST96-13716, AST96-15608, and AST99-81363; Taiwanese grants NSC 86-2112-M-003-T and 89-2112-M-003-004; and the Universities of Illinois, Maryland, and California, Berkeley.