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)."