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IAUC 6448: 1996 P2; C/1995 O1; C/1996 N1

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IAUC number

                                                  Circular No. 6448
Central Bureau for Astronomical Telegrams
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)
Phone 617-495-7244/7440/7444 (for emergency use only)

COMET 1996 P2
     R. H. McNaught, Anglo-Australian Observatory, reports the
discovery by Kenneth S. Russell of a new comet on U.K. Schmidt
plates taken by Fred G. Watson.  The comet has a strong condensation
(m2 about 17) within a 20" coma, and a 20' tail in p.a. 240 deg.
The following positions were measured by McNaught:

     1996 UT             R.A. (2000) Decl.        m1
     Aug. 10.74014    1 40 24.85   -29 51 58.8
          10.80264    1 40 25.78   -29 52 32.6
          11.75125    1 40 39.80   -30 02 11.9    13
          11.79292    1 40 40.36   -30 02 35.5

     R. W. Russell and D. Lynch, The Aerospace Corporation; M.
Hanner, Jet Propulsion Laboratory; and M. Sitko, University of
Cincinnati, report observations of C/1995 O1 on July 22.3 UT with
the Infrared Telescope Facility and the Aerospace infrared
spectrograph between 3 and 13.5 microns.  The 8- to 13.5-micron
spectrum showed a strong silicate emission feature (70 percent
above the continuum), similar to those seen in comets 1P/Halley,
C/1987 P1 (Bradfield), and C/1990 K1 (Levy).  After division by a
blackbody at the continuum temperature, the feature was trapezoidal
with a roughly-flat top from about 9.9 to 11.5 microns and showed
no significant additional spectral structure.  The dust-continuum
color temperature (from fitting a gray body to the 8- and 13-micron
regions) was 200 +/- 10 K, or roughly 50 K warmer than the expected
radiative equilibrium temperature of 145 K for a blackbody at 3.7
AU from the sun.  Due to the cold continuum shape, no detection of
the comet was made in the 3- to 5-micron region.  Brightnesses of
the comet in the 3".4-diameter beam at 8.0, 10.2, and 13.0 microns
were 2, 6, and 5 x 10E-18 W cmE-2 micronE-1 (magnitudes 5.4, 3.2,
and 2.4, respectively).

      Total visual magnitude estimates (cf. IAUC 6435): July 27.27
UT, 8.8 (C. E. Spratt, Victoria, BC, 0.20-m reflector); Aug. 4.90,
8.6 (R. J. Bouma, Groningen, The Netherlands, 0.25-m reflector);
7.24, 8.2 (Spratt); 9.24, 7.9 (Spratt); 10.93, 7.8 (B. H. Granslo,
Fjellhamar, Norway, 0.20-m reflector); 11.24, 7.8 (Spratt); 11.90,
7.6 (Bouma, 15x80 binoculars).

                      (C) Copyright 1996 CBAT
1996 August 12                 (6448)            Daniel W. E. Green

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