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IAUC 7468: 2000cy; C/1999 S4

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                                                  Circular No. 7468
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 617-495-7244/7440/7444 (for emergency use only)

SUPERNOVA 2000cy IN MCG +3-40-2
     T. Puckett, Mountain Town, GA; and D. George, Ottawa, ON,
report the discovery of an apparent supernova (mag 19.5) on an
unfiltered CCD frame (limiting mag 20.5) taken with the Puckett
Observatory 0.60-m automated supernova patrol telescope on July
26.11 UT.  SN 2000cy is located at R.A. = 15h32m14s.75, Decl. =
+18o40'22".9 (equinox 2000.0), which is 29".4 west and 5".7 south
of the center of MCG +3-40-2.  The new object was also present on
an unfiltered CCD frame taken on July 28.09, but does not appear on
Palomar Sky Survey images taken on 1992 June 29 (limiting mag about
21.3) and on 1986 Apr. 12 (limiting mag about 20.2).

     J. Licandro, G. Tessicini, and I. Perez, Centro Galileo
Galilei; and S. Hidalgo, Instituto de Astrofisica de Canarias,
report that the inner coma of C/1999 S4 appears extremely elongated
in the tailward direction on J, H, and K_s images obtained with the
3.6-m Telescopio Nazionale Galileo (+ ARNICA camera) at La Palma on
July 26.9 and 27.9 UT.  There is no clear central condensation, but
the photometric peak appears to move from the anti-tailward border
of the coma toward p.a. 81 deg on July 26.9 and 84 deg on July 27.9,
with a velocity of 7".4/day (26 m/s).  The brightness of the
central coma decreased from J = 8.83 +/- 0.04 on July 26.9 to 9.46
+/- 0.07 on July 27.9, as measured in a 30"-diameter aperture
around the peak.  Color maps do not show any major structure, the
mean colors being J-K = +0.61 +/- 0.05, and H-K = +0.12 +/- 0.06 on
July 26.9.  These data suggest that a major event has occurred in
the nucleus of the comet.
     A. V. Filippenko and R. Chornock, University of California at
Berkeley, report that inspection of a CCD spectrum (range 320-1000
nm) of this comet obtained on July 28 UT with the Shane 3-m
reflector at Lick Observatory reveals no clear emission lines
superposed on the solar reflection spectrum, unlike the case in
spectra they obtained with the same instrument on July 6 and June
27.  There is no evidence for the normally strong CN emission near
380 nm.  The comet's morphology is peculiar, lacking an obvious
head that is brighter than the adjacent tail, although the leading
edge of the head/tail combination is very sharply defined.
     S. Nakano, Sumoto, Japan, writes that A. Asami (Bisei
Spaceguard Center) was unable to find a peak in the comet's
central-condensation brightness to determine an astrometric
position from a CCD image taken in fair conditions on July 28.490
UT with a 0.25-m f/5 reflector.

                      (C) Copyright 2000 CBAT
2000 July 28                   (7468)            Daniel W. E. Green

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