[IAUC] CBET 532: 20060602 : COMET 73P/SCHWASSMANN-WACHMANN

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                                                  Electronic Telegram No. 532
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
      H. Kawakita and H. Kobayashi, Kyoto Sangyo University; M. J.
Mumma, Goddard Space Flight Center, NASA; R. Furusho, Waseda University;
and T.-S. Pyo, T. Fuse, and J. Watanabe, National Astronomical
Observatory of Japan, report:  "We acquired high-dispersion infrared
spectra (resolution 10000 in bands L and M) of fragment 'B' of comet
73P on May 10 UT with the 8-m Subaru telescope (+ InfraRed Camera and
Spectrograph at Mauna Kea.  We detected many emission lines of H_2O
(2.9-micron hot-bands) and OH (prompt emission), 12 lines of HCN
(near 3.0 microns, nu_3 band), six lines of C_2H_6 (near 3.35 microns,
nu_7 band), and two lines of C_2H_2.  The extracted rotational excitation
temperature (T_rot) is about 80 K for HCN.  Based on a simple spherical
coma model, and assuming T_rot = 80 K for all species, we obtain mixing
ratios of H_2O:HCN:C_2H_6:C_2H_2 = 100:0.3:0.2:0.2 in fragment 'B'.
Fragment 'B' was in outburst during our observations (IAUC 8708), so
these mixing ratios probably reflect fresh materials ejected from the
nucleus.  Both fragments 'B' and 'C' were depleted in C_2H_6 (see IAUC
8704, for fragment 'C').  The similar chemistry of fragments 'B' and 'C'
might indicate homogeneity of inner materials in the original nucleus
(before break-up) of comet 73P."


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                         (C) Copyright 2006 CBAT
2006 June 2                      (CBET 532)               Daniel W. E. Green