BIMA Press Release 19970304


First Detection of HCO+ in a Comet, Hale-Bopp (C/1995 01)

FOR RELEASE: 9.00 a.m., March 4, 1997

J. M. Veal and L. E. Snyder (University of Illinois); M. C. H. Wright, J. R. Forster, W. Hoffman, M. W. Pound, I. de Pater, T. Helfer, R. L. Plambeck, G. Engargiola and T. Wong (U. C., Berkeley); L. M. Woodney and M. F. A'Hearn (University of Maryland); P. Palmer (University of Chicago); and Yi-Jehng Kuan (ASIAA, Taiwan)

We report the detection of HCO+ from Comet Hale-Bopp (C/1995 01) using 7 antennas of the Berkeley-Illinois-Maryland-Association Array in autocorrelation mode. The J = 1-0 transition at rest frequency 89.189 GHz was detected in emission on 19, 22, and 28 Feb. UT with peak antenna temperatures (Ta*) equal to 80, 80, and 100 mK, respectively. The HCO+ spectral lines are consistently asymmetric with a redward wing. The full widths at half maximum (not including the redward wing) are equal to 3.0 +/- 0.2, 4.5 +/- 0.2, and 3.0 +/- 0.2 km/sec with line centers (also not including the redward wing) at +1.6 +/- 0.2, +1.8 +/- 0.2, and +1.1 +/- 0.2 km/sec with respect to the comet nucleus, respectively. Relative to the main emission component, the redward wing is about 1/3 the peak temperature and is displaced by approximately +3.7 km/sec from the line center. We believe this to be the first detection of HCO+ in a comet.

Figure (B&W Postscript): HCO+ spectrum of Comet Hale-Bopp.

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