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IAUC 6447: 4U 1735-444; Cyg X-1; N Sgr 1996

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                                                  Circular No. 6447
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
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)
Phone 617-495-7244/7440/7444 (for emergency use only)


4U 1735-444
     R. A. D. Wijnands and M. van der Klis, Astronomical Institute
'Anton Pannekoek', University of Amsterdam; J. van Paradijs,
University of Amsterdam and University of Alabama in Huntsville; W.
H. G. Lewin, Massachusetts Institute of Technology; F. K. Lamb,
University of Illinois, Urbana/Champaign; B. Vaughan, California
Institute of Technology; E. Kuulkers, Astrophysics Division, ESTEC,
European Space Agency; and T. Augusteijn, European Southern
Observatory, report: "RXTE observations of 4U 1735-444 performed on
Aug. 1.60-1.68 UT show a single kHz quasiperiodic oscillation at
frequency 1149 +/- 3 Hz.  The power spectral peak width is 30 +/-
10 Hz and the root-mean-square amplitude 3.1 +/- 0.3 percent (0.24-
18.37 keV).  This is the seventh example of kHz oscillations in a
low-mass x-ray binary."


CYGNUS X-1
     S. N. Zhang, B. A. Harmon, and W. S. Paciesas report for the
Compton Gamma Ray Observatory BATSE team:  "The blackhole candidate
Cyg X-1 is experiencing a transition from a soft state back to its
normal hard state.  It went into the soft state in mid-May,
following a sudden x-ray flux increase in the band 1.3-12 keV (IAUC
6404) and a rapid hard-x-ray-flux decrease in the band 20-200 keV
(IAUC 6405).  Since July 26, its 20- to 200-keV flux increased from
about 200 to about 600 mCrab (as of Aug. 7).  Its energy spectrum
also evolved from a steep power law (photon index about -2.5),
without obvious break up to about 200 keV, to a harder power law
(index about -2.0) with a break at about 100 keV, quite similar to
its hard-state spectrum (typically with index -1.8 and with a break
at 100-150 keV).  If its current trend of hard-x-ray-flux increase
continues, Cyg X-1 will be back to its normal hard state in about a
week."


NOVA SAGITTARII 1996
     Visual magnitude estimates, in part from the AAVSO:  Aug. 5.86
UT, 10.8 (L. Monard, Pretoria, S. Africa); 6.88, 11.0 (J. Ripero
Osorio, Madrid, Spain); 7.22, 10.8 (W. Dillon, Missouri City, TX);
7.93, 11.3 (P. Schmeer, Bischmisheim, Germany); 9.15, 11.2 (Dillon).

                      (C) Copyright 1996 CBAT
1996 August 9                  (6447)            Daniel W. E. Green

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