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IAUC 8681: 2006ao; 73P; V1647 Ori, ASSOCIATED NEBULA; RS Oph

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                                                  Circular No. 8681
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     T. Boles, Coddenham, England, reports the discovery of an
apparent supernova on unfiltered CCD images taken on Mar. 1.069 (at
mag 17.6) and 1.810 UT (at mag 17.4) with a 0.35-m reflector.  The
new object is located at R.A. = 15h59m19s.25, Decl. = +65o13'43".6
(equinox 2000.0; average position from ten images on two nights),
which is approximately 3".1 east and 13".3 south of the center of
the nearest galaxy, which itself is within a small cluster.
Nothing is present at this location on Boles' images from 2005 July
12 and May 11 (limiting mag 19.5) or on Digitized Sky Survey plates
from 1994 May 31 (limiting red mag 20.5) and 1992 June 4 (limiting
blue mag 21.0).

     D. Schleicher, Lowell Observatory, obtained narrowband
photometry of comet 73P on Feb. 25 at r = 1.65 AU using the Hall
1.1-m telescope at Lowell Observatory, with the following averaged
results for component C:  log Q(OH) = 27.30; equivalent log Q(water;
vectorial) = 27.33; log Q(CN) = 24.89; log Q(C_2) = 24.01; log
Af(rho) = 1.7 (cf. IAUC 7342).  For component B:  log Q(OH) = 26.8;
loq Q(water) = 26.8; log Af(rho) = 1.1.  The relative C_2-to-CN
ratio for component C is strongly depleted (by 10 times) with
respect to "normal", as defined by A'Hearn et al. (1995, Icarus 118,
223) -- consistent with the upper-limit result for 73P determined
by Fink and Hicks (1996, Ap.J. 459, 729).  To within relatively
large uncertainties, component B exhibits the same depletion of C_2
as does component C.

     Further to IAUC 8600 and IBVS 5661, several observers recently
have reported the extreme fading of the nebula associated with
V1647 Ori, including B. Reipurth (University of Hawaii), G. M.
Ratto (Pisa, Italy), and P. Corelli (Pagnacco, Italy).  Corelli
writes that his unfiltered CCD frames from Feb. 6 show no nebula to
a limiting stellar mag of 18.  Reipurth remarks that this appears
to confirm its having been a short 'EXor' eruption (cf. IAUC 8289).

     Additional photometry by G. Sostero and E. Guido (cf. IAUC
8673):  Feb. 21.48 UT, V = 7.36, B-V = +0.70; 22.48, 7.43, +0.66;
24.48, 7.70, +0.79; 25.48, 7.75, +0.65; 26.47, 7.76, +0.65; 27.48,
8.04, +0.62.

                      (C) Copyright 2006 CBAT
2006 March 1                   (8681)            Daniel W. E. Green

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