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IAUC 6333: C/1996 B2

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                                                  Circular No. 6333
Central Bureau for Astronomical Telegrams
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
Phone 617-495-7244/7440/7444 (for emergency use only)

     D. Schleicher, Lowell Observatory, communicates:  "Narrow-band
photometry of C/1996 B2 was obtained by R. Millis and myself using
the Hall 1.07-m and the 0.79-m telescopes at Lowell Observatory on
Feb. 25.5 (r = 1.60 AU) and Mar. 1.5 UT (r = 1.51 AU), respectively.
Haser-model production rates for the two dates, respectively, were:
log Q(OH) = 28.68 and 28.73, log Q(CN) = 26.08 and 26.15, and log
Q(C2) = 26.22 and 26.32.  The dust production rates were log
[Af(rho)] = 3.38 and 3.45.  Combining these results with those
previously obtained on Feb. 9.5 at r = 1.90 AU (cf. IAUC 6311)
implies that the OH- and CN-production rates are essentially
unchanged over the three-week time span, while C2 increased by 50
percent and dust production has increased by about 80 percent.
Therefore, while the water-production r dependence is apparently
flat, the species primarily responsible for naked-eye visibility
currently exhibit a production-rate slope of about -2.  This
assumes that any short-term variations are not distorting the true
r dependence, an assumption consistent with recent IUE observations
(see below).
     M. Festou, H. Andernach, M. A'Hearn, M. Haken, G. Moreels, and
J. Clairemidi report for the International Ultraviolet Explorer
(IUE) ToO Team the following observations of C/1996 B2 made at
VILSPA on Feb. 19.3 (r = 1.71 AU), 22.2 (1.66), and 27.2 UT (1.57):
"The production of both water and dust shows no change over the
interval.  Using the same Haser model as that of Schleicher and
Millis (see above), log Q(OH) = 28.68, 28.68, and 28.64, in
remarkably good agreement with their results.  For a 'best'
vectorial model, the corresponding values of Q would be a bit more
than 2 times larger.  The dust production at 300-304 nm can be
characterized by log Af(rho) = 3.17, 3.17, and 3.18 (cf. A'Hearn et
al. 1984, AJ 89, 579).  These values are not directly comparable
with the values found by Schleicher and Millis above, since they
are measured at a different wavelength.  Taken together, they
suggest that the dust has changed from neutral in color to reddish.
CS is also approximately constant over the interval.  This complete
lack of brightening as the comet approaches the sun is just the
behavior that might have been expected for a dynamically new comet,
although the latest orbital solutions (Marsden, IAUC 6329) suggest
that the comet is not dynamically new."

                      (C) Copyright 1996 CBAT
1996 March 4                   (6333)            Daniel W. E. Green

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