共查询到20条相似文献，搜索用时 46 毫秒
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A. Janiuk B. Czerny P. T. &#;ycki 《Monthly notices of the Royal Astronomical Society》2000,318(1):180-186
We present the results of both analytical and numerical calculations of the amplitude of the reflection component in X-ray spectra of galactic black hole systems. We take into account the anisotropy of Compton scattering and the systematic relativistic bulk motion of the hot plasma. In the case of the single scattering approximation, the reflection from the disc surface is significantly enhanced owing to the anisotropy of Compton scattering. On the other hand, the calculations of multiple scattering obtained using the Monte Carlo method show that the anisotropy effect is much weaker in that case. Therefore, the enhanced back-scattered flux may affect the observed spectra only if the disc surface is highly ionized, which reduces the absorption in the energy band corresponding to the first Compton scattering. 相似文献
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Martin Boutelier Didier Barret M. Coleman Miller 《Monthly notices of the Royal Astronomical Society》2009,399(4):1901-1906
We report on a comprehensive analysis of the kilohertz (≥300 Hz) quasi-periodic oscillations (kHz QPOs) detected from the neutron star low-mass X-ray binary 4U 0614+09 with the Rossi X-ray Timing Explorer. With a much larger data set than previously analysed (all archival data from 1996 February up to 2007 October), we first investigate the reality of the 1330 Hz QPO reported by van-Straaten et al. This QPO would be of particular interest since it has the highest frequency reported for any source. A thorough analysis of the same observation fails to confirm the detection. On the other hand, over our extended data set, the highest QPO frequency we measure for the upper kHz QPO is at ∼1224 Hz; a value which is fully consistent with the maximum values observed in similar systems. Secondly, we demonstrate that the frequency dependence of the quality factor ( Q =ν/Δν) and amplitude of the lower and upper kHz QPOs follow the systematic trends seen in similar systems. In particular, 4U 0614+09 shows a drop of the quality factor of the lower kHz QPO above ∼700 Hz. If this is due to an approach to the innermost stable circular orbit, it implies a neutron star mass of ∼1.9 M⊙ . Finally, when analysing the data over fixed durations, we have found a gap in the frequency distribution of the upper QPO, associated with a local minimum of its amplitude. A similar gap is not present in the distribution of the lower QPO frequencies, suggesting some cautions when interpreting frequency ratio distributions, based on the occurrence of the lower QPO only. 相似文献
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A Fundamental Plane of black hole activity 总被引：1，自引：0，他引：1
Andrea Merloni Sebastian Heinz Tiziana Di Matteo 《Monthly notices of the Royal Astronomical Society》2003,345(4):1057-1076
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O. Kotov E. Churazov M. Gilfanov 《Monthly notices of the Royal Astronomical Society》2001,327(3):799-807
It is shown that the energy dependence of the time-lags in Cygnus X-1 excludes any significant contribution of the standard reflected component to the observed lags. The conclusion is valid in the frequency range where time-lags have been detected with sufficient significance. In fact, the data hint that the reflected component is working in the opposite direction, reducing the lags at energies where the contribution of the reflected component is significant.
We argue that the observed logarithmic dependence of time-lags on energy could be due to the small variations of the spectral index in the frame of a very simple phenomenological model. We assume that an optically thin flow/corona, emitting a power law like spectrum, is present at a range of distances from the compact object. The slope of the locally emitted spectrum is a function of distance, with the hardest spectrum emitted in the innermost region. If perturbations with different time-scales are introduced to the accretion flow at different radii, then X-ray lags naturally appear, caused by the inward propagation of perturbations on the diffusion time-scales. 相似文献
We argue that the observed logarithmic dependence of time-lags on energy could be due to the small variations of the spectral index in the frame of a very simple phenomenological model. We assume that an optically thin flow/corona, emitting a power law like spectrum, is present at a range of distances from the compact object. The slope of the locally emitted spectrum is a function of distance, with the hardest spectrum emitted in the innermost region. If perturbations with different time-scales are introduced to the accretion flow at different radii, then X-ray lags naturally appear, caused by the inward propagation of perturbations on the diffusion time-scales. 相似文献
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X-ray reflection spectra from photoionized accretion discs in active galaxies are presented for a wide range of illumination conditions. The energy, equivalent width (EW) and flux of the Fe K α line are shown to depend strongly on the ratio of illuminating flux to disc flux, F x / F disc , the photon index of the irradiating power law, Γ, and the incidence angle of the radiation, i . When F x / F disc ≤2 a neutral Fe K α line is prominent for all but the largest values of Γ. At higher illuminating fluxes an He-like Fe K α line at 6.7 keV dominates the line complex. With a high-energy cut-off of 100 keV, the thermal ionization instability seems to suppress the ionized Fe K α line when Γ≤1.6 . The Fe K α line flux correlates with F x / F disc , but the dependence weakens as iron becomes fully ionized. The EW is roughly constant when F x / F disc is low and a neutral line dominates, but then declines as the line progresses through higher ionization stages. There is a strong positive correlation between the Fe K α EW and Γ when the line energy is at 6.7 keV, and a slight negative one when it is at 6.4 keV. This is a potential observational diagnostic of the ionization state of the disc. Observations of the broad Fe K α line, which take into account any narrow component, would be able to test these predictions. Ionized Fe K α lines at 6.7 keV are predicted to be common in a simple magnetic flare geometry. A model that includes multiple ionization gradients on the disc is postulated to reconcile the results with observations. 相似文献
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M. Gilfanov E. Churazov M. Revnivtsev 《Monthly notices of the Royal Astronomical Society》2000,316(4):923-928
Using RXTE /PCA data, we study the fast variability of the reflected emission in the soft spectral state of Cyg X-1 by means of Fourier frequency-resolved spectroscopy. We find that the rms amplitude of variations of the reflected emission has the same frequency dependence as the primary radiation down to time-scales of ≲30–50 ms. This might indicate that the reflected flux reproduces, with nearly flat response, variations of the primary emission. Such behaviour differs notably from that of the hard spectral state, in which variations of the reflected flux are significantly suppressed in comparison with the primary emission, on time-scales shorter than ∼0.5–1 s.
If related to the finite light-crossing time of the reflector, these results suggest that the characteristic size of the reflector, presumably an optically thick accretion disc, in the hard spectral state is larger by a factor of ≳5–10 than in the soft spectral state. Modelling the transfer function of the disc, we estimate the inner radius of the accretion disc to be Rin ∼100 R g in the hard state and R in ≲10 R g in the soft state for a 10-M⊙ black hole. 相似文献
If related to the finite light-crossing time of the reflector, these results suggest that the characteristic size of the reflector, presumably an optically thick accretion disc, in the hard spectral state is larger by a factor of ≳5–10 than in the soft spectral state. Modelling the transfer function of the disc, we estimate the inner radius of the accretion disc to be R
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R. Barnard S. B. Foulkes C. A. Haswell U. Kolb J. P. Osborne J. R. Murray 《Monthly notices of the Royal Astronomical Society》2006,366(1):287-294
We present results from three XMM–Newton observations of the M31 low mass X-ray binary (LMXB) XMMU J004314.4+410726.3 (Bo 158), spaced over 3 d in 2004 July. Bo 158 was the first dipping LMXB to be discovered in M31. Periodic intensity dips were previously seen to occur on a 2.78-h period, due to absorption in material that is raised out of the plane of the accretion disc. The report of these observations stated that the dip depth was anticorrelated with source intensity. In light of the 2004 XMM–Newton observations of Bo 158, we suggest that the dip variation is due to precession of the accretion disc. This is to be expected in LMXBs with a mass ratio ≲0.3 (period ≲4 h), as the disc reaches the 3:1 resonance with the binary companion, causing elongation and precession of the disc. A smoothed particle hydrodynamics simulation of the disc in this system shows retrograde rotation of a disc warp on a period of ∼11 P orb , and prograde disc precession on a period of 29 ± 1 P orb . This is consistent with the observed variation in the depth of the dips. We find that the dipping behaviour is most likely to be modified by the disc precession, hence we predict that the dipping behaviour repeats on an 81 ± 3 h cycle. 相似文献
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In this paper we present a fully relativistic approach to modelling both the continuum emission and the reflected fluorescent iron line from a primary X-ray source near a Kerr black hole. The X-ray source is located above an accretion disc orbiting around the black hole. The source is assumed to be a static point source located on an arbitrary position above the disc, on or off the axis of rotation. We carry out Monte Carlo simulations in order to estimate the iron line spectrum as well as its equivalent width. Because of the gravitational lensing effect, an enhancement of the iron line is expected when the primary source is located close to the central black hole. We find that for a source located on the axis of rotation the enhancement is relatively modest. An observer at inclination 30° would measure an equivalent width of ∼300 eV in the extreme case of a maximally rotating black hole and a source located at height 1.5 gravitational radii from the centre. This corresponds to an equivalent width enhancement factor of about 2 compared with the classical value where no lensing effect comes into play. However, when allowing the source to be located off the axis of rotation, much stronger enhancement can be obtained. In the extreme case of a maximally rotating black hole and a source located just above the approaching side of the disc, an observer at inclination 30° could measure an equivalent width as high as ∼1.5 keV (i.e., ∼10 times the classical value). We also find that observers located at high inclination angles observe a stronger line than observers at low inclination angles. 相似文献
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