1,950 research outputs found
Bernoulli equation and the nonexistence of maximal jets
We discuss the idea of maximal jets introduced by Falcke & Biermann in 1995.
According to it, the maximum possible jet power in its internal energy equals
the kinetic power in its rest mass. We show this result is incorrect because of
an unfortunate algebraic mistake.Comment: A&A, in pres
Reflection and noise in the low spectral state of GX339-4
We analyze RXTE/PCA observations of GX339-4 in the low spectral state from
1996--1997 and show that the pattern of its spectral and temporal variability
is nearly identical to that of Cyg X-1. In particular, a tight correlation
exists between the QPO centroid frequency and the spectral parameters. An
increase of the QPO centroid frequency is accompanied with an increase of the
amplitude of the reflected component and a steepening the slope of the
underlying power law. Fourier frequency resolved spectral analysis showed, that
the variability of the reflected component at frequencies higher than ~1-10 Hz
is suppressed in comparison with that of the primary emission.Comment: 4 pages, 4 figures. Accepted in Astronomy and Astrophysics Main
Journa
Compton scattering as the explanation of the peculiar X-ray properties of Cyg X-3
We consider implications of a possible presence of a Thomson-thick,
low-temperature, plasma cloud surrounding the compact object in the binary
system Cyg X-3. The presence of such a cloud was earlier inferred from the
energy-independent orbital modulation of the X-ray flux and the lack of high
frequencies in its power spectra. Here, we study the effect of Compton
scattering by the cloud on the X-ray energy and power spectra, concentrating on
the hard spectral state. The process reduces the energy of the high-energy
break/cut-off in the energy spectra, which allows us to determine the Thomson
optical depth. This, together with the observed cut-off in the power spectrum,
determines the size of the plasma to be 2x10^9 cm. At this size, the cloud will
be in thermal equilibrium in the photon field of the X-ray source, which yields
the cloud temperature of 3 keV, which refines the determination of the Thomson
optical depth to 7. At these parameters, thermal bremsstrahlung emission of the
cloud becomes important as well. The physical origin of the cloud is likely to
be collision of the very strong stellar wind of the companion Wolf-Rayet star
with a small accretion disc formed by the wind accretion. Our model thus
explains the peculiar X-ray energy and power spectra of Cyg X-3.Comment: MNRAS, the version as printed, the title and abstract change
A classification of the X-ray and radio states of Cyg X-3 and their long-term correlations
We present a detailed classification of the X-ray states of Cyg X-3 based on
the spectral shape and a new classification of the radio states based on the
long-term correlated behaviour of the radio and soft X-ray light curves. We
find a sequence of correlations, starting with a positive correlation between
the radio and soft X-ray fluxes in the hard spectral state, changing to a
negative one at the transition to soft spectral states. The temporal evolution
can be in either direction on that sequence, unless the source goes into a very
weak radio state, from which it can return only following a major radio flare.
The flare decline is via relatively bright radio states, which results in a
hysteresis loop on the flux-flux diagram. We also study the hard X-ray light
curve, and find its overall anticorrelation with the soft X-rays. During major
radio flares, the radio flux responds exponentially to the level of a hard
X-ray high-energy tail. We also specify the detailed correspondence between the
radio states and the X-ray spectral states. We compare our results to those of
black-hole and neutron-star binaries. Except for the effect of strong
absorption and the energy of the high-energy break in the hard state, the X-ray
spectral states of Cyg X-3 closely correspond to the canonical X-ray states of
black-hole binaries. Also, the radio/X-ray correlation closely corresponds to
that found in black-hole binaries, but it significantly differs from that in
neutron-star binaries. Overall, our results strongly support the presence of a
black hole in Cyg X-3.Comment: MNRAS, in pres
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