Central Bureau for Astronomical Telegrams
IAUC 5576: Cyg X-1; N Sgr 1992 No. 2
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Circular No. 5576
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
CYGNUS X-1
A. Vikhlinin, R. Sunyaev, E. Churazov, M. Gilfanov, J. Ballet,
M. Denis, P. Laurent, and J. P. Roques, on behalf of the Granat
team (Space Research Institute, Moscow; Service d'Astrophysique du
CEA, Saclay; Centre d'Etude Spatiale des Rayonnements, Toulouse),
report: "Transient, low-frequency (about 0.04 Hz), quasi-periodic
oscillations (QPO) of flux 40-70 keV from the black-hole candidate
Cygnus X-1 have been found during several SIGMA observations in
1990-1992. When the QPO feature is absent, the power density
spectrum exhibits typical flattening below 0.1 Hz with respect to the
extrapolation of high-frequency flickering noise. The appearance
of the QPO feature and the oscillation frequency seem to be correlated
with the 40- to 70-keV flux. This is the fourth black-hole
candidate where QPO phenomena have been detected. Previously,
transient QPO of x-ray flux were seen by ART-P onboard Granat from
the black-hole candidates Nova Mus 1991 (GRS 1121-68 = 1124-684;
cf. IAUC 5161, 5176) and GX 339-4; Ginga had similar detections
from LMC X-1, GRS 1124-68, and GX 339-4 (IAUC 4653)."
C. Kouveliotou, University Space Research Association; M. H.
Finger, Computer Sciences Corportation; G. J. Fishman, C. A.
Meegan, and R. B. Wilson, Marshall Space Flight Center, NASA; and
W. S. Paciesas, University of Alabama at Huntsville, report for the
BATSE team: "Quasi-periodic oscillations have been detected in the
soft-gamma-ray flux from Cygnus X-1 observed by the BATSE instrument
of the Compton Observatory. Fourier power spectra show a
broad QPO feature centered on a frequency of about 0.04 Hz. The
feature has been detected independently in the 20- to 60-keV, 60-
to 110-keV, and 110- to 320-keV energy bands on several different
occasions. Searches for correlations of the QPO behavior with
other source characteristics are presently being conducted."
NOVA SAGITTARII 1992 No. 2
Further photometry by A. C. Gilmore, Mt. John University
Observatory (cf. IAUC 5566): July 30.46 UT, V = 10.12 +/- 0.01, B-V
= +0.25 +/- 0.01, U-B = -0.63 +/- 0.01, V-R = +1.03 +/- 0.02, V-I =
+0.93 +/- 0.06.
W. Liller, Vina del Mar, Chile, communicates the following
additional unfiltered CCD magnitudes (cf. IAUC 5564): July 28.02 UT,
9.41; 31.01, 9.80; Aug. 1.00, 9.72; 2.97, 9.55 (comparison stars
SAO 186744 and 186758).
1992 August 4 (5576) Daniel W. E. Green
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