Circular No. 6366

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                                                  Circular No. 6366




Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
Phone 617-495-7244/7440/7444 (for emergency use only)


COMET C/1996 B2 (HYAKUTAKE)
     M. J. Mumma, M. A. DiSanti, N. Dello Russo, and D. X. Xie,
Goddard Space Flight Center, NASA; M. Fomenkova, University of
California at San Diego; and K. Magee-Sauer, Rowan College of New
Jersey, report the detection of various parent molecules in C/1996
B2 on Mar. 23 and 24 UT, using the CSHELL cryogenic infrared
spectrometer at the NASA Infrared Telescope Facility on Mauna Kea:
"A partial listing of the species, the vibrational bands, and the
detected lines follows:   H2O [111-100, 8 ortho-lines, and 5 para-
lines], HDO [nu(sub)1, 3 lines], CO [1-0, 8 lines, J = 0-6], CH4
[nu(sub)3, 2 lines, R0 and R(superscript)-(1)], CH3OH [nu(sub)3, Q-
branch, resolved], C2H6 [nu(sub)7, rQ(sub)0- and rQ(sub)1-branches],
HCN [nu(sub)3, 7 lines, J = 1-6], and OCS [nu(sub)1 band, 5 lines].
NH3 is provisionally detected in the a- and s-Q-branches (nu(sub)1).
C2H2, H2CO, and HC3N were searched for but not detected.  Numerous
unidentified lines are present.  All lines appear peaked on the
nucleus, and those of H2O, CO, CH4, and C2H6 extend to the ends of
the east-west slit, about 15" or 1000 km in either direction.  A
preliminary analysis of three lines of H2O (2(sub)02-3(sub)03,
2(sub)11-3(sub)12, and 2(sub)12-3(sub)13) measured on Mar. 24.5
suggests a rotational temperature about 70 K within a 1" x 1".4 box
centered on the nucleus.  The flux measured for the 2(sub)02-
3(sub)03 line was 4.8 x 10E-18 watt/mE2 within that aperture,
corresponding to Q(H2O) = 1.5 x 10E29 molecules/s.  Two branches of
the ethane nu(sub)7 band were detected on Mar. 24.5, and are
extended along the slit; they appear peaked on the nucleus and
exhibit the spatial profile expected for a parent volatile.  The
flux for the rQ(sub)0-branch (2983.4 cmE-1) was 2.4 x 10E-17
watt/mE2, and that for the rQ(sub)1-branch was 2.8 x 10E-17
watt/mE2, in a 1" x 1".4 box centered on the nucleus.  Assuming
fluorescence excitation of the rQ(sub)0 upper levels from the K = 0
and K = 2 lower levels, the combined production rate for molecules
in those levels is 2.2 x 10E26 molecules/s.  Fluorescence
excitation of the upper levels of rQ(sub)1 leads to a combined
production rate for molecules in the K = 1 and K = 3 lower levels
of 2.6 x 10E26 molecules/s.  Their sum (4.8 x 10E26 molecules/s) is
a lower bound to the total production rate for C2H6 in K = 0-3.  If
the K-ladders exhibit a 130-K distribution, then the total
production rate could be larger by about 3.  The mixing ratio for
C2H6 is 0.3 percent in the observed states alone."
     Naked-eye m1 estimates:  Mar. 30.14 UT, 1.5 (M. V. Zanotta,
Monte Generoso, Italy); 30.88, 1.7 (A. Diepvens, Balen, Belgium);
31.22, 1.5 (R. Keen, Mt. Thorodin, CO); 31.79, 1.9 (J. Ticha, Klet,
Czech Republic).

                      (C) Copyright 1996 CBAT
1996 April 1                   (6366)            Daniel W. E. Green