Black Hole Cygnus Research Articles

X-ray polarization properties of partially ionized equatorial obscurers around accreting compact objects

ABSTRACT We present the expected X-ray polarization signal resulting from distant reprocessing material around black holes. Using a central isotropic power-law emission at the centre of the simulated model, we add distant equatorial and axially symmetric media that are covering the central accreting sources. We include partial ionization and partial transparency effects, and the impact of various polarization and steepness of the primary radiation spectrum. The results are obtained with the Monte Carlo code STOKES that considers both line and continuum processes and computes the effects of scattering and absorption inside static homogenous wedge-shaped and elliptical toroidal structures, varying in relative size, composition and distance to the source. We provide first order estimates for parsec-scale reprocessing in Compton-thin and Compton-thick active galactic nuclei, as well as winds around accreting stellar-mass compact objects, for observer’s inclinations above and below the grazing angle. The resulting reprocessed polarization can reach tens of per cent with either parallel or perpendicular orientation with respect to the axis of symmetry, depending on subtle details of the geometry, density, and ionization structure. We also show how principal parameters constrained from X-ray spectroscopy or polarimetry in other wavelengths can lift the shown degeneracies in X-ray polarization. We provide an application example of the broad modelling discussion by revisiting the recent IXPE 2–8 keV X-ray polarimetric observation of the accreting stellar-mass black hole in Cygnus X-3 from the perspective of partial transparency and ionization of the obscuring outflows.

New Constraints on the Spin of the Black Hole Cygnus X-1 and the Physical Properties of its Accretion Disk Corona

We present a new analysis of NuSTAR and Suzaku observations of the black hole Cygnus X-1 in the intermediate state. The analysis is performed using kerrC, a new model for analyzing spectral and spectropolarimetric X-ray observations of black holes. kerrC builds on a large library of simulated black holes in X-ray binaries. The model accounts for the X-ray emission from a geometrically thin, optically thick accretion disk, the propagation of the X-rays through the curved black hole spacetime, the reflection off the accretion disk, and the Comptonization of photons in coronae of different 3D shapes and physical properties before and after the reflection. We present the results from using kerrC for the analysis of archival NuSTAR and Suzaku observations taken on 2015 May 27–28. The best wedge-shaped corona gives a better fit than the cone-shaped corona. Although we included cone-shaped coronae in the funnel regions above and below the black hole to resemble to some degree the common assumption of a compact lamppost corona hovering above and/or below the black hole, the fit chooses a very large version of this corona that makes it possible to Comptonize a sufficiently large fraction of the accretion disk photons to explain the observed power-law emission. The analysis indicates a black hole spin parameter a (−1 ≤ a ≤ 1) between 0.861 and 0.921. The kerrC model provides new insights into the radial distribution of the energy flux of returning and coronal emission irradiating the accretion disk. kerrC furthermore predicts small polarization fractions around 1% in the 2–8 keV energy range of the recently launched Imaging X-ray Polarimetry Explorer.

ВЛИЯНИЕ ЗАРЯДА В ЧЕРНОЙ ДЫРЕ БАРДИНА НА ЗАДЕРЖКУ ВРЕМЕНИ ПРИБЫТИЯ СИГНАЛОВ

In this paper we consider an impact of Bardeen black hole charge on times of arrival of signals on the time delay caused by frame-dragging effect. This effect can arise in astrophysical systems, where one of the companions of the binary system emits a variable electromagnetic signal. A variable signal travels on both sides of a rotating object in the equatorial plane. We consider a spherically symmetric regular black hole by Bardeen as a rotating object, which has a deviation parameter g besides mass M and spin a. This parameter is related to the described nonlinear electrodynamics, and the Bardeen metric reduces to the Kerr metric when g = 0. We investigate times of arrival of signals effect in a realistic final lens system in a Bardeen black hole compared to a Kerr–Newman black hole. It is noteworthy that an influence of electric charge on the time delay in the Kerr–Newman black hole appears in the second and third orders, and an influence of the charge in the Bardeen black hole only in the third order. The contribution of the leading-order time delay with the capabilities of modern equipment is fundamentally measurable, however, the influence of the charge manifests itself only in the third, therefore, this study is more of academic interest than practical. For the binary system pulsar – black hole Cygnus X-1, numerical values were tabulated.

New measurement for the stellar mass black hole in Cygnus X-1

<p indent=0mm>The study on stellar mass black holes is an important issue in astrophysics. Over the past decades, astronomers have confirmed some stellar mass black holes and determined their physical properties via the observations of the X-ray binaries and the gravitational waves emitted from the mergers of binary black holes. Recently, a research team re-measured the precise distance of Cygnus X-1 (an X-ray binary) and subsequently derived the values of the mass, spin, and other properties of the black hole V1357 Cyg in Cygnus X-1. The results show that the mass of Cygnus X-1 is (21.2 ± 2.2) <italic>M</italic>_⊙, indicating that V1357 is the most massive stellar mass black hole in X-ray binaries, thus challenging the existing models of massive stellar binary evolution. The future precise measurements of similar black holes in X-ray binaries would further deepen our understanding of the stellar evolution models as well as the physical properties of stellar mass black holes.

Re-estimating the Spin Parameter of the Black Hole in Cygnus X-1

Abstract Cygnus X-1 is a well-studied persistent black hole X-ray binary. Recently, the three parameters needed to estimate the black hole spin of this system, namely the black hole mass M, the orbital inclination i, and the source distance D, have been updated. In this work we redetermine the spin parameter using the continuum-fitting technique for those updated parameter values. Based on the assumption that the spin axis of the black hole is aligned with the orbital plane, we fit the thermal disk component to a fully relativistic thin accretion disk model. The error in the spin estimate arising from the combined observational uncertainties is obtained via Monte Carlo simulations. We demonstrate that, without considering the counteracting torque effect, the new spin parameter is constrained to be a * &gt; 0.9985 (3σ), which confirms that the spin of the black hole in Cygnus X-1 is extreme.

A physical model for the spectral-timing properties of accreting black holes

We develop new techniques to deconvolve the radial structure of the X-ray emission region in the bright low/hard state of the black hole Cygnus X-1 using both spectral and timing data in the 3-35~keV range. The spectrum at these energies is dominated by Comptonisation rather than the disc, but there is a complex pattern in the time lags between different energy bands and differences in the normalisation and shape in the power spectra of these bands, which clearly shows that the Comptonisation is not produced from a single, homogeneous region. We use a physically based model of density fluctuations propagating through a spectrally inhomogeneous flow, setting the spectral components by jointly fitting to the time-averaged and Fourier resolved spectra. The predicted variability in any band is modelled analytically in Fourier space so it can be fit directly to the observed power spectra and lags. We find that the best fit model picks out three distinct radii in the flow, each with a distinct Compton spectrum. The variability and luminosity produced at these radii is enhanced, while propagation of fluctuations from larger radii is suppressed. We associate these radii with the disc truncation, the inner edge of the flow, and (more speculatively) the jet launch radius. These distinct radii are most evident where the source is close to a transition between the low/hard and high/soft states. We suggest that the smoother power spectra seen at lower luminosities imply that the source structure is simpler away from the transition.

A new window on black hole accretion

Recent polarization measurements of the stellar-mass black hole in Cygnus X-1 reveal an extended corona in the inner parts of the accretion flow and open the path for a new era in high-energy astrophysics.

Discovery of a Luminous Radio Transient 460 pc from the Central Supermassive Black Hole in Cygnus A

Abstract We report the appearance of a new radio source at a projected offset of 460 pc from the nucleus of Cygnus A. The flux density of the source (which we designate Cygnus A-2) rose from an upper limit of &lt;0.5 mJy in 1989 to 4 mJy in 2016 (ν = 8.5 GHz), but is currently not varying by more than a few percent per year. The radio luminosity of the source is comparable to the most luminous known supernovae, it is compact in Very Long Baseline Array observations down to a scale of 4 pc, and it is coincident with a near-infrared point source seen in pre-existing adaptive optics and HST observations. The most likely interpretation of this source is that it represents a secondary supermassive black hole in a close orbit around the Cygnus A primary, though an exotic supernova model cannot be ruled out. The gravitational influence of a secondary SMBH at this location may have played an important role in triggering the rapid accretion that has powered the Cygnus A radio jet over the past 107 years.

X-ray probes of black hole accretion disks for testing the no-hair theorem

The spins of a number of supermassive and stellar-mass black holes have been measured based on detections of thermal continuum emission and relativistically broadened iron lines in their x-ray spectra. Likewise, quasiperiodic variability has been observed in several sources. Such measurements commonly make the assumption that black holes are described by the Kerr metric, which according to the no-hair theorem characterizes black holes uniquely in terms of their masses and spins. This fundamental property of black holes can be tested observationally by measuring potential deviations from the Kerr metric introduced by a parametrically deformed Kerr-like spacetime. Thermal spectra, iron lines, and variability have already been studied extensively in several such metrics, which usually depend on only one particular type of deviation or contain unphysical regions outside of the compact object. In this paper, I study these x-ray probes in the background of a new Kerr-like metric which depends on four independent deviation functions and is free of pathological regions outside of the event horizon. I show that the observed signals depend significantly on primarily two types of deviations and that the strong correlation between the spin and the deviation parameters found previously in other Kerr-like metrics is partially broken for rapidly spinning black holes. This suggests that high-spin sources are the best candidates for tests of the no-hair theorem with x-rays and I obtain first constraints on such deviations from the stellar-mass black hole Cygnus X-1.

A complex state transition from the black hole candidate Swift J1753.5−0127

We present our monitoring campaign of the outburst of the black-hole candidate Swift J1753.5-0127, observed with the Rossi X-ray Timing Explorer and the Swift satellites. After ~4.5 years since its discovery, the source had a transition to the hard intermediate state. We performed spectral and timing studies of the transition showing that, unlike the majority of the transient black holes, the system did not go to the soft states but it returned to the hard state after a few months. During this transition Swift J1753.5-0127 features properties which are similar to those displayed by the black hole Cygnus X-1. We compared Swift J1753.5-0127 to one dynamically confirmed black hole and two neutron stars showing that its power spectra are in agreement with the binary hosting a black hole. We also suggest that the prolonged period at low flux that followed the initial flare is reminiscent of that observed in other X-ray binaries, as well as in cataclysmic variables.

The broad iron Kαline of Cygnus X-1 as seen byXMM-Newtonin the EPIC-pn modified timing mode

We present the analysis of the broadened, flourescent iron Kalpha line in simultaneous XMM-Newton and RXTE data from the black hole Cygnus X-1. The XMM-Newton data were taken in a modified version of the timing mode of the EPIC-pn camera. In this mode the lower energy threshold of the instrument is increased to 2.8 keV to avoid telemetry drop outs due to the brightness of the source, while at the same time preserving the signal-to-noise ratio in the Fe Kalpha band. We find that the best-fit spectrum consists of the sum of an exponentially cut off power-law and relativistically smeared, ionized reflection. The shape of the broadened Fe Kalpha feature is due to strong Compton broadening combined with relativistic broadening. Assuming a standard, thin accretion disk, the black hole is close to rotating maximally.

Polarized Gamma-Ray Emission from the Galactic Black Hole Cygnus X-1

Because of their inherently high flux allowing the detection of clear signals, black hole x-ray binaries are interesting candidates for polarization studies, even if no polarization signals have been observed from them before. Such measurements would provide further detailed insight into these sources' emission mechanisms. We measured the polarization of the gamma-ray emission from the black hole binary system Cygnus X-1 with the International Gamma-Ray Astrophysics Laboratory Imager on Board the Integral Satellite (INTEGRAL/IBIS) telescope. Spectral modeling of the data reveals two emission mechanisms: The 250- to 400-keV (kilo-electron volt) data are consistent with emission dominated by Compton scattering on thermal electrons and are weakly polarized. The second spectral component seen in the 400-keV to 2-MeV band is by contrast strongly polarized, revealing that the MeV emission is probably related to the jet first detected in the radio band.

Astro Dub Morphologies

ABSTRACTIn the text artists Anna Piva and Edward George discuss ideas, processes and practices that informed the making of Astro Black Morphologies/Astro Dub Morphologies, a multimedia installation and sound performance created using transformed X-ray data from the black hole Cygnus X-1. In 2002 in a talk titled ‘The Music of Black Holes’, astrophysicist Phil Uttley at Southampton University announced that Cygnus X-1's X-ray emissions were implicitly musical in structure. Piva and George, working with astronomer Tim O'Brien from Jodrell Bank Observatory and generative designer Adrian Ward, transformed the data from this mysterious deep space phenomenon into an immersive dub space experience.

VHE GAMMA-RAYS FROM GALACTIC X-RAY BINARY SYSTEMS

The detection of TeV gamma-rays from LS 5039 and the binary pulsar PSR B1259–63 by HESS, and from LS I +61 303 and the stellar-mass black hole Cygnus X-1 by MAGIC, provides clear evidence of very efficient acceleration of particles to multi-TeV energies in X-ray binaries. These observations demonstrate the richness of nonthermal phenomena in compact galactic objects containing relativistic outflows or winds produced near black holes and neutron stars. I review here some of the main observational results on very high energy (VHE) γ-ray emission from X-ray binaries, as well as some of the proposed scenarios to explain the production of VHE γ-rays. I put special emphasis on the flare TeV emission, suggesting that the flaring activity might be a common phenomena in X-ray binaries.

Astro Black Morphologies: Music and Science Lovers

Acompressed series of possible histories of science in modern music, the text outlines the themes of poetic and historic correspondences between music, cosmology and the body that informed the making of Astro Black Morphologies/Astro Dub Morphologies, a multimedia installation and live sound-art performance by Flow Motion in which data from possible black hole Cygnus X1 is transformed into an immersive electronic sound-and-image environment.

Revealing the Focused Companion Wind in Cygnus X‐1 withChandra

We have analyzed a Chandra HETGS spectrum of the Galactic black hole Cygnus X-1, obtained at a source flux that is approximately twice that commonly observed in its persistent low-intensity, spectrally hard state. We find a myriad of absorption lines in the spectrum, including H- and He-like resonance lines from Ne, Na, Mg, and Si. We calculate a flux-weighted mean redshift of 100 km s-1 and a flux-weighted mean velocity width of 800 km s-1 (FWHM) for lines from these elements. We also detect a number of transitions from Fe XVIII-XXIV and Ni XIX-XX in absorption; however, the identification of these lines is less certain and a greater range of shifts and breadth is measured. Our observation occurred at a binary phase of 0.76; the lines observed are consistent with absorption in an ionized region of the supergiant O9.7 Iab companion wind. The spectrum is extremely complicated: a rather large range of temperatures is implied, and it is unlikely that a narrow range of ionization parameters can account for the lines observed. Prior Chandra HETGS spectra of Cygnus X-1 were obtained in a similar transition state (at 0.93) and in the low/hard state (at 0.84). Considered together, these spectra provide evidence for a companion wind that is focused as it flows onto the black hole primary in this system.

Long term variability of Cyg X-1

We study the long term evolution of the relationship between the root mean square (rms) variability and flux (the ``rms-flux relation'') for the black hole Cygnus X-1 as monitored from 1996 to 2003 with the Rossi X-ray Timing Explorer (RXTE). We confirm earlier results by Uttley & McHardy (2001) of a linear relationship between rms and flux in the hard state on time scales > 5 s reflecting in its slope the fractional rms variability. We demonstrate the perpetuation of the linear rms-flux relation in the soft and the intermediate state. The existence of a non-zero intercept in the linear rms-flux relation argues for two lightcurve components, for example, one variable and one non-variable component, or a possible constant rms component. The relationship between these two hypothesized components can be described by a fundamental dependence of slope and intercept at time scales ~< 10 ksec with long term averages of the flux.

Spectroscopy of the near-nuclear regions of Cygnus A: estimating the mass of the supermassive black hole

We use a combination of high spatial resolution optical and near-infrared spectroscopic data to make a detailed study of the kinematics of the narrow-line region (NLR) gas in the near-nuclear regions of the powerful, FRIIradio galaxy Cygnus A (z = 0.0560), with the overall goal of placing limits on the mass of any supermassive black hole in the core. Our K-band infrared observations (0.75-arcsec seeing) - taken with NIRSPEC on the Keck II telescope - show a smooth rotation pattern across the nucleus in the Paa and H 2 emission lines along a slit position (PA180°) close to perpendicular to the radio axis, however, there is no evidence for such rotation along the radio axis (PA105°). Higher spatial resolution observations of the [O III] λ5007 emission line -- taken with STIS on the Hubble Space Telescope (HST) - confirm the general rotation pattern of the gas in the direction perpendicular to the radio axis, and provide evidence for steep velocity gradients within a radius of 0.1 arcsec of the core - corresponding to the high surface brightness structure visible in high-resolution narrow-band images. The [O IH] line remains broad throughout the core region (FWHM ∼ 300-900 km s - 1 ), but the spatial distribution of [O III] provides no evidence for an unresolved inner narrow-line region (INLR). Assuming that the ionized gas is circularly rotating in a thin disc and that the large linewidths are due to activity-induced turbulence, the circular velocities measured from both the Keck and HST data lead to an estimate of the mass of the supermassive black hole of 2.5 ′ 0.7 x 10 9 M O .. For the host galaxy properties of Cygnus A, this mass is consistent with the global correlations between black hole mass and host galaxy properties deduced for non-active galaxies. Therefore, despite the extreme power of its radio source and the quasar-like luminosity of its active galactic nucleus (AGN), the black hole in Cygnus A is not unusually massive considering the luminosity of its host galaxy. Indeed, the estimated mass of the black hole in Cygnus A is similar to that inferred for the supermassive black hole in the FRI radio galaxy M87, despite the fact that the AGN and radio jets of Cygnus A are two to three orders of magnitude more powerful. Overall, these results are consistent with the idea that the properties and powers of the AGN in radio galaxies are determined as much by the mass accretion rates as by the absolute masses of their supermassive black holes. As well as providing evidence for a supermassive black hole in the core of Cygnus A, our data also demonstrate that nuclear activity has an important effect on the kinematics of the circumnuclear gas on a subkiloparsec scale. Most notably, the velocity offsets measured in the two outer HST/STIS slit positions are consistent with the presence of an activity-induced outflow in the NW cone.

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.

The Stellar X-Ray Polarimeter for the Spectrum-X-Gamma Mission

AbstractWe describe an X-ray polarimeter which will be flown on the SPECTRUM-X-Gamma mission. The instrument exploits three distinct physical processes to measure polarization: Bragg reflection from a graphite crystal, Thomson scattering from a metallic lithium target, and photoemission from a Cesium Iodide photocathode. These three processes allow polarization measurements over an energy band of 0.3 keV to 12 keV. The polarimeter will make possible sensitive measurements of several hundred known X-ray sources. X-ray polarization measurements will allow us to constrain the geometry of gas flow in X-ray binaries, identify nonthermal emission in supernova remnants, test current models for X-ray emission in radio pulsars, determine the radiation mechanisms in active galactic nuclei, and search for inertial frame dragging (Lense-Thirring effect) around the putative black hole in Cygnus X-1.