[IAUC] CBET 594: 20060812 : COMET 73P/SCHWASSMANN-WACHMANN

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                                                  Electronic Telegram No. 594
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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COMET 73P/SCHWASSMANN-WACHMANN
     M. L. Sitko, University of Cincinnati and Space Science Institute;
R. W. Russell, D. K. Lynch, and R. Ford, The Aerospace Corporation; H. B.
Hammel, Space Science Institute; and W. Golisch and P. Sears, Infrared
Telescope Facility (IRTF), NASA, report on post-perihelion observations
made of comet 73P's component 'C' using the IRTF (+ BASS) on August 5,
7, and 8 UT.  The comet exhibited a continuum between 3 and 13 microns,
on top of which a silicate emission band from 8.5 to 12.2 microns was
observed.  The flux observed on all three days was approximately the
same to within 10 percent.  An underlying blackbody, normalized to the
continuum fluxes of the averaged spectra at 8.1 and 12.5 microns,
yielded a mean grain temperature of 272 K, with an estimated uncertainty
of +/- 5 K.  The derived temperature was between 10 and 11 percent higher
than that of an equivalent blackbody at the heliocentric distance of the
comet.  The feature-to-continuum ratio in the silicate band was 1.19,
smaller than that previously reported for this fragment from
pre-perihelion observations (IAUCs 8701 and 8717).  The measured flux
between 10.0 and 11.0 microns, using the 3".4 circular entrance aperture
of BASS, was 0.28 +/- 0.03 Jy (equivalent magnitude m_N = 5.4 +/- 0.1).


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                         (C) Copyright 2006 CBAT
2006 August 12                   (CBET 594)               Daniel W. E. Green