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IAUC 7365: Cyg X-3; SW UMa; 1999gq

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                                                  Circular No. 7365
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
     M. L. McCollough and G. J. Fishman, Marshall Space Flight
Center, for the Compton Gamma Ray Observatory (CGRO) BATSE team;
and E. B. Waltman, Naval Research Laboratory, report: "The galactic
jet source Cygnus X-3 has been exhibiting very low flux levels in
radio and hard x-rays (20-100 keV) since Feb. 4.  Such behavior
usually precedes major radio flaring episodes, with radio fluxes >
3 Jy (McCollough et al. 1999, Ap.J. 517, 951).  Very low radio
fluxes of < 30 mJy have been observed at 2 GHz with the Green Bank
Interferometer between Feb. 4 and 9.  Daily averages for Jan. 29-
Feb. 11 of the hard-x-ray flux, measured using the BATSE/CGRO
earth-occultation technique, have been below the 1-day detection
limit of about 100 mCrab.  Previous observations of Cyg X-3 with
periods of very-low-radio and hard-x-ray flux, having durations
from days to a few weeks, are followed by major radio flares.  The
last such episode occurred in 1997 (IAUC 6673).  Target-of-
opportunity observations have been initiated for both RXTE and CGRO.
Observations at other wavelengths are encouraged during the next
few weeks."


SW URSAE MAJORIS
     J. A. Mattei, AAVSO, reports that this cataclysmic variable is
in outburst for the first time since its 20-day superoutburst in
Oct. 1997 (IAUC 6760), when the AAVSO International Database shows
that the star reached mean mag 10.7 at maximum.  R. Zissell, South
Hadley, MA, found SW UMa at CCD V = 16.55 on Feb. 9.192 UT.
Selected visual magnitude estimates forwarded by Mattei:  Feb.
11.243, [15.6 (G. Hanson, Cave Creek, AZ); 11.926, 14.1 (C. Jones,
Laindon, Essex, England); 12.028, 12.4 (P. Schmeer, Saarbruecken,
Germany); 12.126, 11.5 (S. Tracy, North Granby, CT); 12.74, 10.7 (J.
Gunther, Peyrins, France); 13.060, 10.5 (J. Bortle, Stormville, NY);
14.044, 10.5 (G. Poyner, West Midlands, England).


SUPERNOVA 1999gq IN NGC 4523
     Unfiltered CCD magnitudes:  1999 Dec. 25.806 UT, 15.1 (S.
Yoshida and K. Kadota, Ageo, Saitama, Japan); 2000 Jan. 21.191,
14.97 (M. Suarez, Las Palmas, Canary Islands); 28.701, 15.0
(Yoshida and Kadota).

                      (C) Copyright 2000 CBAT
2000 February 14               (7365)            Daniel W. E. Green

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