Electronic Telegram No. 594 Central Bureau for Astronomical Telegrams INTERNATIONAL ASTRONOMICAL UNION M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A. IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions) CBAT@CFA.HARVARD.EDU (science) URL http://cfa-www.harvard.edu/iau/cbat.html 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). NOTE: These 'Central Bureau Electronic Telegrams' are sometimes superseded by text appearing later in the printed IAU Circulars. (C) Copyright 2006 CBAT 2006 August 12 (CBET 594) Daniel W. E. Green