Electronic Telegram No. 70
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 C/2001 Q4 (NEAT)
     S. M. Brafford, University of Dayton; M. L. Sitko,
University of Cincinnati; and R. W. Russell and D. L.
Kim, The Aerospace Corporation, report 3-13-micron
spectrophotometry of comet C/2001 Q4, obtained on May 31.2
UT with the Mt. Lemmon 1.5-m University of Minnesota telescope
(+ Aerospace Broadband Array Spectrograph System; 8".5 aperture;
49"chop throw; integration times 10 min on the comet and 20 min
on the reference star, alpha Lyr):  "A smooth comet continuum
was seen to rise from 3.5 to 8.4 microns, beyond which a strong
silicate emission band was observed.  An underlying blackbody
continuum with a temperature of about 345 +/- 10 K was fit
to the continuum flux at 5, 8.4, and 12 microns.  This grain
temperature is about 24 percent higher than that of an
equilibrium blackbody at the heliocentric distance of the comet,
and higher than that observed on May 14.1 (IAUC 8342) using the same
instrument and telescope when the comet was closer to the sun.
Structure is seen in the silicate feature, including emission peaks
at 10.5 and 11.2 microns.  The silicate-feature-to-continuum ratio
was about 1.43 +/- 0.04, lower than that reported on May 14.2.
No scattered solar flux was detected at the shorter wavelengths
after subtracting the thermal continuum.  With our aperture, the
comet has the following narrowband (about 0.25 micron) magnitudes
and combined random errors (due to calibration star and comet, as
well as variations due to the presence of real spectral structure):
[3.7 microns] = 6.8 +/- 0.3, [4.7 microns] = 4.60 +/- 0.11, [5
microns] = 4.27 +/- 0.06, [8 microns] = 1.71 +/- 0.06, [10.5
microns] = -0.54 +/- 0.02, and [12 microns] = -0.49 +/- 0.03
(the stated errors are standard deviations of the mean)."


NOTE: These 'Central Bureau Electronic Telegrams' are intended to
      be preliminary announcements of items that later appear in the
      formal IAU Circulars.  Citations should normally be made to IAUCs
      rather than to CBETs.

                         (C) Copyright 2004 CBAT
2004 June 5                       (CBET 70)               Daniel W. E. Green