Central Bureau for Astronomical Telegrams
IAUC 6590: C/1995 O1
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Circular No. 6590
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, 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)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)
COMET C/1995 O1 (HALE-BOPP)
C. M. Wright, Max-Planck-Institut fur Extraterrestrische
Physik (MPE); C. H. Smith, University College, Australian Defence
Force Academy; A. Krabbe, MPE; T. Lehmann, University of Jena; and
T. Boeker, Space Telescope Science Institute, report: "Images in a
broad-band 8-13-micron filter (N band) with the MPG/ESO 2.2-m
telescope (+ mid-infrared camera MANIAC) on 1996 Oct. 28.8, 30.8,
31.8, and Nov. 1.8 UT show a clear fan-shaped structure extending
about 30" in length, with a symmetry axis pointing almost due east.
The size and orientation appeared stable over all four nights, and
there was no obvious jet activity. N-band fluxes in a 21".6-
diameter aperture were 14.7 +/- 0.3, 16.7 +/- 0.1, 18.4 +/- 0.1,
and 18.0 +/- 0.1 x 10E-17 W cmE-2 micronE-1, respectively, on the
four nights. Images in a broad-band 17.3-22.7-micron filter (Q
band) on Oct. 30.8 and 31.8 and Nov. 1.8 showed a morphology
consistent with that in the N band; Q-band fluxes (21".6 aperture)
were 16.0 +/- 0.2, 12.6 +/- 0.3, and 14.8 +/- 0.4 x 10E-17 W cmE-2
micronE-1. (Uncertainties are statistical; absolute calibration is
about 30 percent). N-to-Q color temperatures (with no correction
for silicate emission) on Oct. 30.8, 31.8, and Nov. 1.8 were 207,
233, and 218 +/- 15 K, respectively. We see little evidence for
variability. On Nov. 1.8, fluxes in a 21".6-diameter aperture in
narrow-band 8.025-, 10.53-, and 12.95-micron filters were 2.1 +/-
0.5, 11.1 +/- 0.4, and 7.2 +/- 0.3 x 10E-17 W cmE-2 micronE-1,
respectively. The 8.0-13.0-micron color temperature is 188 +/- 12
K, only marginally above the 175 K expected from a blackbody in
radiative equilibrium at 2.5 AU from the sun. The silicate feature,
as judged from the 10.5-micron data, is a factor of 2.1 +/- 0.2
above the 188 K continuum."
A. Lovell, P. Schloerb, C. DeVries, J. Dickens, W. Irvine, and
M. Senay, University of Massachusetts, write: "Maps (field size 4'
x 4'; resolution 1') obtained during Mar. 11-13 with the FCRAO 14-m
antenna (+ focal-plane array receiver) of the HCN J=1-0, CS J=2-1,
and HCO+ J=1-0 transitions show that HCN and CS emission peaks at
the position of the nucleus, but the HCO+ emission is highly
asymmetric (peaking at a point offset 1'.5 from the nucleus in p.a.
about 320 deg; anti-sunward direction was about p.a. 340 deg).
There is a small HCN extension toward the p.a. of peak HCO+
brightness. The HCN and CS lines have widths of 2.0 km/s and are
centered on the velocity of the nucleus. However, the HCO+ line is
broader at the nucleus position (width 3.2 km/s), and it is
redshifted by 1.0 km/s. The HCO+ line width increases to 4.1 km/s
at its peak-intensity position, and there is a small increase in
the observed redshift of about 0.2 km/s."
(C) Copyright 1997 CBAT
1997 March 17 (6590) Daniel W. E. Green
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