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M.R. Hogerheijde, I. de Pater, M.C.H. Wright, W. Hoffman (UC Berkeley), R. Forster (Hat Creek Radio Obs.), L.E. Snyder, A. Remijan (Univ. of Illinois, Urbana-Champaign), L.M. Woodney (Lowell Obs.), M.F. A'Hearn (Univ. of Maryland), P. Palmer (Univ. of Chicago), Y.-J. Kuan, H.-C. Huang (ASIAA/National Taiwan Normal Univ.), G.A. Blake, C. Qi, J. Kessler, S.-Y. Liu (Caltech)
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~\sigma 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.
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