Searches for Heavy Molecules in Comet C/1995 O1 Hale-Bopp

P. Pratap (MIT Haystack Observatory), A. Lovell, C. De Vries, J. Dickens, W. Irvine, P. Schloerb, M. Senay (FCRAO, Univ. of Mass. Amherst)

We present results of line searches carried out at 7 mm and 1.3 cm wavelength, using the Haystack Observatory 37-m antenna. The focus of this observing campaign was on searches for heavy molecules, with large moments of inertia, where the partition function of the molecule may favor observations at low frequencies. A successful detection was made of the CH tex2html_wrap_inline11 OH 7(0)-6(1) A+ transition at 44 GHz, with peak antenna temperature of approximately 70 mK km/s on March 28, 1997. However, other searches were unsuccessful, and only upper limits were obtained for C tex2html_wrap_inline11 H tex2html_wrap_inline15 3(2,1)-3(1,2), CS 1-0, CCS 4,3-3,2, HC tex2html_wrap_inline11 N 5-4, HC tex2html_wrap_inline19 N 18-17, NH tex2html_wrap_inline11 1(1)-1(1), and NH tex2html_wrap_inline11 3(3)-3(3). Three-sigma limits are 13 mK km/s for C tex2html_wrap_inline11 H tex2html_wrap_inline15 , 8 mK km/s for CCS, 9 mK km/s for HC tex2html_wrap_inline11 N, 15 mK km/s for HC tex2html_wrap_inline19 N, and 18 mK km/s for NH tex2html_wrap_inline11 3(3)-3(3). Assuming a rotational temperature of 70 K, the production rate for HC tex2html_wrap_inline11 N is log Q[HC tex2html_wrap_inline11 N] < 27.5, consistent with the detection reported by Lis et al. on IAUC 6566. For CH tex2html_wrap_inline11 OH, assuming thermal equilibrium at 100 K, log Q[CH tex2html_wrap_inline11 OH] = 29.5.