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IAUC 7393: Cyg X-3; BC UMa; C/2000 F1

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                                                  Circular No. 7393
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7244/7440/7444 (for emergency use only)


CYGNUS X-3
     D. Dal Fiume, E. Palazzi, and M. Orlandini, ITESRE, CNR,
Bologna; and L. Nicastro and S. Del Sordo, IFCAI, CNR, Palermo, on
behalf of a large collaboration, write:  "BeppoSAX observed Cyg X-3
on Mar. 21.779-22.599 UT for about 30 000 s during an extended
radio and hard-x-ray quenched state (IAUC 7365).  The source is
well detected in the PDS instrument up to 140 keV at a flux level
of about 10 mCrab.  A quick analysis shows major and complex
changes in the emitted x-ray spectrum when compared to the normal
quiescent radio state.  Measured source fluxes in given energy
bands:  7 x 10**-9 erg s**-1 cm**-2, 2-10 keV; 4.6 x 10**-10,
10-20; 1.2 x 10**-10, 20-100.  A 10-percent systematic error in
these fluxes must be added due to a rather poor spectral fit.  No
model that we previously used gave a satisfactory fit.  For
comparison, the fluxes measured during the quiescent radio state in
Sept. 1997 in the same energy bands were respectively 2.9 x 10**-9,
1.8 x 10**-9, and 1.7 x 10**-9 erg s**-1 cm**-2.  Additional
BeppoSAX observations are planned."


BC URSAE MAJORIS
     E. O. Waagen, AAVSO, reports that this SU UMa-type cataclysmic
variable is in outburst for the first time since July 1995,
according to observations in the AAVSO International Database, with
the following recent visual magnitude estimates showing that the
present event is likely a superoutburst:  Mar. 26.870 UT, [14.0 (E.
Muyllaert, Oostende, Belgium); 27.256, [15.3 (G. Hanson, Cave Creek,
AZ); 28.80, [13.7 (P. Schmeer, Bischmisheim, Germany); 31.799, 12.1
(Schmeer); 31.836, 11.3 (T. Kinnunen, Espoo, Finland); Apr. 1.06,
11.0 (G. Dyck, Assonet, MA); 2.139, 11.6 (Muyllaert); 3.255, 12.1
(Hanson); 4.013, 13.1 (Schmeer).


COMET C/2000 F1 (SOHO)
    D. A. Biesecker, SM&A Corporation and Goddard Space Flight
Center, reports observations (measured by D. Hammer and himself,
reduced by B. G. Marsden) of another Kreutz sungrazing comet found
by M. Meyer and J. D. Shanklin via the SOHO website.  The comet was
observed in both the LASCO C2 and C3 telescopes and showed clear
evidence for a tail.  Astrometry and orbital elements appear on
MPEC 2000-G18.

     2000 UT           R.A. (2000) Decl.
     Mar. 31.846      0 55.4       + 3 34

                      (C) Copyright 2000 CBAT
2000 April 4                   (7393)            Daniel W. E. Green

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