Central Bureau for Astronomical Telegrams
IAUC 4153: CH Cyg; V1341 Cyg
The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).
Read IAUC 4154
Circular No. 4153
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
TWX 710-320-6842 ASTROGRAM CAM Telephone 617-495-7244/7440/7444
CH CYGNI
K. Panov, M. Ivanova, and B. Kovachev, Department of Astronomy
and National Astronomical Observatory, Bulgarian Academy of Sciences,
telex that their photoelectric observations of CH Cyg indicate
the possible beginning of a new 'activity phase' following its
minimum in Aug. and Sept.: Aug. 17 UT, U = 7.38, U-B = +0.97; Dec. 9,
U = 7.31; U-B = -0.21.
V1341 CYGNI
G. Hasinger, A. Langmeier, M. Sztajno, and W. Pietsch, Max-
Planck-Institut fur Extraterrestrische Physik; and M. Gottwald,
EXOSAT Observatory, European Space Operations Center, telex: "Recent
EXOSAT observations of V1341 Cyg (= Cyg X-2) give evidence for
two different types of quasi-periodic oscillations (QPOs). During
Oct. 28.654-29.158 UT, intensity-dependent QPOs, with centroid
frequencies between 18 and 42 Hz and low-frequency noise, were again
present (cf. IAUC 4070), while the source luminosity (at 8 kpc)
changed from ~ 0.9 to 1.4 x 10**31 J/s. These QPOs had a hard
spectrum: the rms equivalent sinsusoidal pulsed fraction increased
steadily with energy from 4.0 +/- 0.3 percent at 2 keV to 9.9 +/- 0.4
percent near 10 keV. In a hardness-versus-intensity diagram, the
source was on the 'horizontal branch' (constant hardness ratio with
increasing intensity). Below a luminosity of 1.2 x 10**31 J/s, we
simultaneously observed a second peak in the power spectra. It is
conceivable that this is a second harmonic; however, its centroid
frequency was only a factor of 1.82 +/- 0.04 higher than the principal
peak. It had an rms pulsed fraction that was typically a factor
of 2 lower. A further observation of V1341 Cyg during Nov.
15.028-15.535 showed the source in an active state with flares at
high energies, at a luminosity of 1.2 x 10**31 J/s, which was changing
by only 6 percent. The brightening of the source was associated
with a large increase in spectral hardness. In this state, we
detected QPOs with a centroid frequency of 5.64 +/- 0.08 Hz, which
was independent of source intensity within errors (cf. IAUC 4087).
The rms pulsed fraction was variable on a timescale of hours, with
a maximum value of 2.6 +/- 0.1 percent. These QPOs had a soft
spectrum; their rms pulsed fraction was 4.3 +/- 0.1 percent at 2 keV
and < 2.5 percent above 4.5 keV (2-sigma)."
1985 December 20 (4153) Daniel W. E. Green
Read IAUC 4154
Our Web policy. Index to the CBAT/MPC/ICQ pages.
