Black Hole In Cyg Research Articles

LONG-TERM MONITORING OF THE BLACK HOLE CANDIDATE SWIFT J1753.5–0127 WITHINTEGRAL/SPI

The black hole candidate Swift J1753.5-0127 went into outburst in 2005 June. Rather than fade into quiescence as most black-hole-candidate transients do, it has remained in a low hard spectral state for most of the $\sim$ 9 years after outburst. The persistent emission while in a hard state is reminiscent of the black hole Cyg X-1 and the black hole candidates 1E 1740.7-2942 and GRS 1758-258. Thus far hard X-ray/soft gamma-ray results have focused mainly on the 2005 flare, with a few additional observations during 2007. Here, we present results from INTEGRAL/SPI observations from 2005 - 2010 spanning the 22 - 650 keV energy range. Spectral analysis shows a weak high-energy excess ( $\sim$ 2.9 $\sigma$) above a cutoff powerlaw model that is well fit by a powerlaw suggesting an additional spectral component. Observations of Cyg X-1, 1E 1740.7-2942, and GRS 1758-258 have shown similar spectra requiring an additional high-energy component The SPI results are compared to previously reported results for Swift J1753.5-0127 as well as observations of other sources.

Long term variability of Cygnus X-1

We present a scheme for determining the spectral state of the canonical black hole Cyg X-1 using data from previous and current X-ray all sky monitors (RXTE-ASM, Swift-BAT, MAXI, and Fermi-GBM). Determinations of the hard/intermediate and soft state agree to better than 10% between different monitors, facilitating the determination of the state and its context for any observation of the source, potentially over the lifetimes of different individual monitors. A separation of the hard and the intermediate states, which strongly differ in their spectral shape and short-term timing behavior, is only possible when data in the soft X-rays (<5 keV) are available. A statistical analysis of the states confirms the different activity patterns of the source (e.g., month- to year-long hard-state periods or phases during which numerous transitions occur). It also shows that the hard and soft states are stable, with the probability of Cyg X-1 remaining in a given state for at least one week to be larger than 85% in the hard state and larger than 75% in the soft state. Intermediate states are short lived, with a 50% probability that the source leaves the intermediate state within three days. Reliable detection of these potentially short-lived events is only possible with monitor data that have a time resolution better than 1 d.

On the determination of the spin of the black hole in Cyg X-1 from X-ray reflection spectra

The spin of Cygnus X-1 is measured by fitting reflection models to Suzaku data covering the energy band 0.9–400 keV. The inner radius of the accretion disc is found to lie within 2 gravitational radii (rg=GM/c2), and a value of is obtained for the dimensionless black hole spin. This agrees with recent measurements using the continuum fitting method by Gou et al. and of the broad iron line by Duro et al. The disc inclination is measured at ⁠, which is consistent with the recent optical measurement of the binary system inclination by Orosz et al. of 27°± 0°.8. We pay special attention to the emissivity profile caused by irradiation of the inner disc by the hard power-law source. The X-ray observations and simulations show that the index q of that profile deviates from the commonly used, Newtonian, value of 3 within 3rg, steepening considerably within 2rg, as expected in the strong gravity regime.

ERRATUM: “SEARCH FOR CHAOS IN NEUTRON STAR SYSTEMS: IS Cyg X-3 A BLACK HOLE?” (2010, ApJ, 708, 862)

The accretion disk around a compact object is a nonlinear general relativistic system involving magnetohydrodynamics. Naturally the question arises whether such a system is chaotic (deterministic) or stochastic (random) which might be related to the associated transport properties whose origin is still not confirmed. Earlier, the black hole system GRS 1915+105 was shown to be low dimensional chaos in certain temporal classes. However, so far such nonlinear phenomena have not been studied fairly well for neutron stars which are unique for their magnetosphere and kHz quasi-periodic oscillation (QPO). On the other hand, it was argued that the QPO is a result of nonlinear magnetohydrodynamic effects in accretion disks. If a neutron star exhibits chaotic signature, then what is the chaotic/correlation dimension? We analyze RXTE/PCA data of neutron stars Sco X-1 and Cyg X-2, along with the black hole Cyg X-1 and the unknown source Cyg X-3, and show that while Sco X-1 and Cyg X-2 are low dimensional chaotic systems, Cyg X-1 and Cyg X-3 are stochastic sources. Based on our analysis, we argue that Cyg X-3 may be a black hole.

SEARCH FOR CHAOS IN NEUTRON STAR SYSTEMS: IS Cyg X-3 A BLACK HOLE?

The accretion disk around a compact object is a nonlinear general relativistic system involving magnetohydrodynamics. Naturally, the question arises whether such a system is chaotic (deterministic) or stochastic (random) which might be related to the associated transport properties whose origin is still not confirmed. Earlier, the black hole system GRS 1915+105 was shown to be low-dimensional chaos in certain temporal classes. However, so far such nonlinear phenomena have not been studied fairly well for neutron stars which are unique for their magnetosphere and kHz quasi-periodic oscillation (QPO). On the other hand, it was argued that the QPO is a result of nonlinear magnetohydrodynamic effects in accretion disks. If a neutron star exhibits chaotic signature, then what is the chaotic/correlation dimension? We analyze RXTE/PCA data of neutron stars Sco X-1 and Cyg X-2, along with the black hole Cyg X-1 and the unknown source Cyg X-3, and show that while Sco X-1 and Cyg X-2 are low dimensional chaotic systems, Cyg X-1 and Cyg X-3 are stochastic sources. Based on our analysis, we argue that Cyg X-3 may be a black hole.

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.

Rms–flux relation of Cyg X-1 with RXTE: dipping and nondipping cases

The rms (root mean square) variability is the parameter for understanding the emission temporal properties of X-ray binaries (XRBs) and active galactic nuclei (AGN). The rms-flux relation with Rossi X-ray Timing Explorer (RXTE) data for the dips and nondip of black hole Cyg X-1 has been investigated in this paper. Our results show that there exist the linear rms-flux relations in the frequency range 0.1-10 Hz for the dipping light curve. Moreover, this linear relation still remains during the nondip regime, but with the steeper slope than that of the dipping case in the low energy band. For the high energy band, the slopes of the dipping and nondipping cases are hardly constant within errors. The explanations of the results have been made by means of the ``Propagating Perturbation'' model of Lyubarskii (1997).

Probing the Inflow/Outflow and Accretion Disk of Cygnus X‐1 in the High State with theChandraHigh Energy Transmission Grating

Cygnus X-1 was observed in the high state at the conjunction orbital phase (0) with Chandra High Energy Transmission Grating (HETG). Strong and asymmetric absorption lines of highly ionized species were detected, such as Fe xxv, Fe xxiv, Fe xxiii, Si xiv, S xvi, Ne x, etc. In the high state the profile of the absorption lines is composed of an extended red wing and a less extended blue wing. The red wings of higher ionized species are more extended than those of lower ionized species. The detection of these lines provides a way to probe the properties of the flow around the companion and the black hole in Cyg X-1 during the high state. A broad emission feature around 6.5 keV was significantly detected from the spectra of both the Chandra/HETG and the RXTE/Proportional Counter Array. This feature appears to be symmetric and can be fitted with a Gaussian function rather than the Laor disk line model of the fluorescent Fe K(alpha) line from an accretion disk. The implications of these results on the structure of the accretion flow of Cyg X-1 in the high state are discussed.

Resolving the Composite Fe Kα Emission Line in the Galactic Black Hole Cygnus X‐1 withChandra

We observed the Galactic black hole Cyg X-1 with the Chandra High Energy Transmission Grating Spectrometer for 30 ks on 2001 January 4. The source was in an intermediate state, with a flux that was approximately twice that commonly observed in its persistent low/hard state. Our best-fit model for the X-ray spectrum includes narrow Gaussian emission line (E = 6.415 ? 0.007 keV, FWHM= 80 eV, W = 16 eV) and broad-line (E = 5.82 keV, FWHM= 1.9 keV, W = 140 eV) components, and a smeared edge at 7.3 ? 0.2 keV (? ~ 1.0). The broad-line profile is not as strongly skewed as those observed in some Seyfert galaxies. We interpret these features in terms of an accretion disk with irradiation of the inner disk producing a broad Fe K? emission line and edge, and irradiation of the outer disk producing a narrow Fe K? emission line. The broad line is likely shaped predominantly by Doppler shifts and gravitational effects, and to a lesser degree by Compton scattering due to reflection. We discuss the underlying continuum X-ray spectrum and these line features in the context of diagnosing the accretion flow geometry in Cyg X-1 and other Galactic black holes.

Discovery of Kilohertz Fluctuations in Centaurus X‐3: Evidence for Photon Bubble Oscillations (PBO) and Turbulence in a High‐Mass X‐Ray Binary Pulsar

We report the discovery of kilohertz fluctuations, including quasiperiodic oscillations (QPO) at {approx}330 Hz (260-407 Hz) and {approx}760 Hz (671-849 Hz) and a broadband kilohertz continuum in the power-density spectrum of the high-mass X-ray binary pulsar Centaurus X-3. These observations of Cen X-3 were carried out with the Rossi X-Ray Timing Explorer (RXTE). The fluctuation spectrum is flat from millihertz to a few hertz, then steepens to f{sup -2} behavior between a few hertz and {approx}100 Hz. Above 100 Hz, the spectrum shows the QPO features, plus a flat continuum extending to {approx}1200 Hz and then falling out to {approx}1800 Hz. These results, which required the co-adding three days of observations of Cen X-3, are at least as fast as the fastest known variations in X-ray emission from an accreting compact object (kilohertz QPO in LMXB sources) and probably faster since extension to {approx}1800 Hz is indicated by the most likely parameterization of the data. Multidimensional radiation hydrodynamics simulations of optically thick plasma flow onto the magnetic poles of an accreting neutron star show that the fluctuations at frequencies above 100 Hz are consistent with photon bubble turbulence and oscillations (PBO) previously predicted to be observable in this source. Wemore » show that previous observations of Cen X-3 constrain the models to depend on only one parameter, the size of the polar cap. For a polar cap opening angle of 0.25 radians (polar cap radius {approx}2.5 km and area {approx}20 km2, for a neutron star radius of 10 km), we show that the spectral form above 100 Hz is reproduced by the simulations, including the frequencies of the QPO and the relative power in the QPO and the kilohertz continuum. This has resulted in the first model-dependent measurement of the polar cap size of an X-ray pulsar. The simulations underpredict the overall amplitude of the observed spectrum, which we suggest is the consequence of a two-dimensional axisymmetric simulation of an intrinsically three-dimensional phenomenon. The power-density spectrum of Cen X-3 shows a dramatic decrease above {approx}1000 Hz, which suggests an optical depth {approx}30 across the accretion mound consistent with effects of radiative diffusion in the simulations. We identify this decline at high frequency as the first direct evidence of radiative diffusion near the surface of a neutron star (NS). We suggest the fluctuations observed at frequencies below 100 Hz, whose spectrum has a different form from that of the kilohertz phenomena, reflect intermittency in the mass transfer mechanism that carries plasma from the accretion disk to field aligned flow onto the neutron star's polar caps. Using simple estimates based on Rayleigh-Taylor instabilities, possibly modulated by intrinsic disk turbulence, we show that mass transfer in ''blobs'' forming through Rayleigh-Taylor disruption of the disk's inner edge can explain the large amplitude fluctuations required by the spectrum at frequencies f{approx}1 Hz, but only if magnetic pressure in the disk's innermost regions inflates the disk until its scale height is comparable to the magnetosphere's size {approx}4300 km. The observational results required the development of a procedure for the careful determination of the dead-time effects of the PCA. This procedure is described in Appendix A. As a consequence of the use of observations of Cyg X-1 for the estimation of dead-time corrections for the observations of Cen X-3, we have also demonstrated that the black hole Cyg X-1 shows clear evidence of variability up to a frequency of {approx}280 Hz. Also observations of GX 17+2 were used to validate the procedure for dead-time corrections. This analysis of GX 17+2 clearly indicates the presence of a kilohertz QPO and the absence of any significant simultaneous kilohertz continuum. (c) 2000 The American Astronomical Society.« less

No Massive Black Hole in Cygnus X‐3

There has been a recent suggestion that Cyg X-3 contains a black hole (BH) of mass M1 ~ 17 M☉. This interpretation is closely linked to a previous claim that Cyg X-3 contains a Wolf-Rayet star of mass M2 ~ 10 M☉. The latter interpretation would imply that the X-ray source in this close binary (P = 4.8 hr) is enshrouded by a relatively cool superstrong wind with ≥10−5 M☉ yr-1. It can be shown that such a wind would be completely opaque to the low-energy X-rays observed from the source, and hence the Wolf-Rayet hypothesis cannot be a correct one. By pursuit of the same argument, it also follows that the compact object must be of modest mass, ruling out the existence of a massive BH in Cyg X-3. Note, however, that at present we cannot strictly rule out the probable existence of a stellar-mass BH in Cyg X-3 or any other X-ray binary that is believed to contain a neutron star as the compact object. Yet a more probable scenario for Cyg X-3 would be one where the compact object is a canonical neutron star and the companion is an extremely low mass dwarf, M2 ~ 10-2 M☉, much like PSR 1957+20.

Stellar And Solar X-Ray Polarimetry

The theory of Bragg crystal x-ray polarimeters is presented to-gether with an analysis of the statistics of photon-limited polarimeters. The focusing Bragg crystal polarimeter flown on the OSO-8 Satellite is described and a number of results obtained at 2.6 keV and 5.2 keV are presented. A polarimeter of this type with at least ten times the area is needed to answer a number of astrophysically interesting questions. A discussion is given of a Compton scattering polarimeter that is expected to be useful of energies above 40 keV. It is shown how this polarimeter may be used to test for the presence of a black hole in Cyg X-1. A solar flare x-ray polarimeter that is scheduled to be flown on an early space shuttle mission is described and an estimate is given of its sensitivity.

Observational test for the existence of a rotating black hole in Cyg X-1

X-RAY satellite experiments1,13,14 are now investigating the degree and plane of linear polarisation of the radiation from Cyg X-1. This radiation can be explained as coming from an accretion disk around a black hole, the polarisation of the X rays being due to electron scattering in the hotter, inner regions of the disk. Novick reported2 observing 3% linear polarisation (marginally significant at the 2.5σ level) at 2.6 keV from Cyg X-1. Existing predictions of the polarisation properties, as a function of energy, have been based on a Newtonian approximation3–5, thus neglecting gravitational effects on the rays as they propagate from the disk's surface to an observer at infinity. We present here preliminary results of a full general-relativistic calculation which show that gravitational effects completely alter the polarisation properties, and provide a sensitive test of the existence of a black hole.

Origin of the black hole in Cyg X-1

THE evidence that Cygnus X-1 is a black hole of mass ≳ 9M⊙ (ref. 1) is not conclusive, but is sufficient to warrant some consideration of the implications of such an object for the late stages of stellar evolution. We argue here that such a black hole must form directly by implosion of a star of mass ≳ 30M⊙ rather than by accretion on to a neutron star. The Galaxy may contain ∼ 107 such massive black holes.