Central Bureau for Astronomical Telegrams
IAUC 6568: C/1995 O1; 1997 CU26
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Circular No. 6568
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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COMET C/1995 O1 (HALE-BOPP)
M. J. Mumma, M. A. DiSanti, and N. Dello Russo, Goddard Space
Flight Center, NASA; K. Magee-Sauer, Rowan College of New Jersey;
and M. Fomenkova, University of California at San Diego, report:
"We detected parent volatiles in C/1995 O1 on 1996 Dec. 10-12 and
1997 Jan. 21.5 UT, using the NASA Infrared Telescope Facility (+
CSHELL cryogenic infrared spectrometer) on Mauna Kea. The species,
the vibrational bands, and the detected lines are: CO [1-0, 10
lines, J' = 0-7]; C2H6 [nu7, rQ0- and rQ1-branches]; five lines of
H2O were also detected. All lines are peaked on the nucleus, and
all are extended; CO extends nearly to the ends of the east-west
slit, about 15" in either direction. CH4 nu3 R0 was searched for
on Dec. 11.1 but was not detected. The following reductions refer
to a box 1" x 1".4 centered on the nucleus. On Jan. 21.5, the
rotational temperature for CO was about 130 K, and the production
rate was about 3.2 x 10E29 molecules/s. The peak CO line flux
measured was 8.7 x 10E-17 W mE-2 in R4. A preliminary analysis of
five lines of H2O suggests a rotational temperature about 40-100 K.
For 70 K, we derive Q(H2O) = 5 x 10E30 molecules/s. The flux for
the rQ0-branch (2983.4 cmE-1) was 6.9 x 10E-18 W mE-2, and that for
the rQ1-branch was 8.8 x 10E-18 W mE-2. Assuming fluorescence
excitation of the rQ0 upper levels from the K = 0 and K = 2 lower
levels, the combined production rate for molecules in those levels
is 2.8 x 10E27 molecules/s. Fluorescence excitation of the upper
levels of rQ1 leads to a combined production rate of 3.6 x 10E27
molecules/s for molecules in the K = 1 and K = 3 lower levels.
Their sum (6.4 x 10E27 molecules/s) is a lower bound to the total
production rate for C2H6. The mixing ratios are then H2O:CO:C2H6 =
100:6.4:0.13 on Jan. 21.5. If the K-ladders exhibit a 130-K
distribution like CO, the total ethane-production rate could be
larger by about 3. On Dec. 11.1, the rotational temperature for CO
was about 70 K, and the production rate was 2 x 10E29; for C2H6,
the production rate in K = 0-3 was 7.1 x 10E27."
1997 CU26
R. P. Binzel, Massachusetts Institute of Technology, report
that measurements of the visible spectrum (range 450-950 nm) of
the probable Centaur 1997 CU26 (cf. MPEC 1997-D11), obtained on
Feb. 25.2 UT using the 2.4-m Hiltner telescope of the MDM
Observatory at Kitt Peak, show a spectral slope similar to that of
an average D-type asteroid.
(C) Copyright 1997 CBAT
1997 February 25 (6568) Daniel W. E. Green
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