Electronic Telegram No. 491
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)
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COMET 73P/SCHWASSMANN-WACHMANN
     D. Schleicher, Lowell Observatory, obtained narrowband photometry
of comet 73P on Apr. 25 at r = 1.13 AU using the Hall 1.1-m telescope
at Lowell Observatory, with the following averaged results:
Component C:  log Q(OH) = 27.75; equivalent log Q(water; vectorial) =
27.86; log Q(CN) = 25.22; log Q(C_2) = 24.49; log Af(rho) = 2.3 (cf.
IAUC 7342).
Component B:  log Q(OH) = 27.48; loq Q(water) = 27.59;
log Q(CN) = 25.06; log Q(C_2) = 24.24; log Af(rho) = 1.5.
Component G:  log Q(OH) = 26.58; loq Q(water) = 26.69;
log Q(CN) = 24.15; log Q(C_2) = 23.33; log Af(rho) = 0.5.
All three components show strong depletions (7-9 times) in the C_2-to-CN
ratio relative to "typical" as defined by A'Hearn et al. (1995, Icarus
118, 223).  The dust-to-gas ratios, based on Af(rho) vs. OH, for
components B and G are much lower (3-4 times) than for the primary
component, C.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2006 CBAT
2006 April 29                    (CBET 491)               Daniel W. E. Green