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IAUC 7633: 2001bt; 1999 KW4; C/1999 T2; N Aql 2001

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                                                  Circular No. 7633
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)

SUPERNOVA 2001bt IN IC 4830
     R. Chassagne, Ste. Clotilde, Ile de Reunion, reports the discovery of an
apparent supernova (mag about 15.0) on unfiltered CCD images taken with a
0.30-m f/2.7 telescope on May 24.0 and 24.9 UT.  The object is located at
R.A. = 19h13m46s.75, Decl. = -59o17'22".8 (equinox 2000.0), which is 27".7
west and 17".1 north of the nucleus of IC 4830.  An image of the same field
taken on May 5.0 showed nothing at this position (limiting mag 19).  The
U.K. Schmidt image in the Digital Sky Survey (1975 May 10.7 UT) also showed
nothing at this position (limiting mag 21).

1999 KW4
     P. Pravec and L. Sarounova, Ondrejov Observatory, report:
"Our photometric observations of this object (cf. IAUC 7632) on
six nights during 2000 June 19.0-27.9 UT revealed a generally nonperiodic
lightcurve, the minima repeating on a characteristic interval of about 1.5 hr
with amplitudes 0.1-0.2 mag.  This suggests that a slightly elongated primary
rotates with a period of about 3 hr, the deviations from strict periodicity
perhaps being caused by the rotation lightcurve of and/or mutual occultations
involving a secondary component (Pravec et al. 2000, Icarus 146, 190; see
also Sinnott 2001, Sky Tel. 100, No. 6, 100).  Extensive observations during
this apparition are needed to describe the unusual photometric behavior and
to estimate the parameters of the binary system."

     K. Hornoch, Lelekovice, Czech Republic, reports observations (0.35-m
reflector + CCD) of an antitail on several occasions during the past month:
Apr. 24.89 UT, 4'.0 long in p.a. 51 deg; May 10.92, 3'.0, 46 deg; 20.95, 5'.0,
57 deg; 24.94, 7', 50 deg.  The main tail ranged from 1'.1 in p.a. 150 deg on
Apr. 24 to 1'.5 in p.a. 175 deg on May 20; on May 24 there was a second broad
tail 1'.8 long in p.a. 104 deg, a very bright 0'.6 jet in p.a. 270 deg and a
much fainter 0'.5 jet in p.a. 200 deg.  CCD observations by J. Manteca,
Barcelona, Spain (0.31-m Schmidt-Cassegrain), on May 23.00 put this comet at
R = 15.0.

     CCD photometry: May 20.07 UT, V = 13.33 +/- 0.08 (P. Sobotka, Brno,
Czech Republic; comparison GSC 1048.174: V = 14.52 by A. Henden); 23.07,
13.43 +/- 0.05 (Sobotka); 24.19, 13.42 +/- 0.1 (J. D. West, Mulvane, KS).

                      (C) Copyright 2001 CBAT
2001 May 25                    (7633)              Brian G. Marsden

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