Search Results for « Black-hole X-ray binary »

We present a unified semiquantitative model for the disc–jet coupling in black hole X-ray binary systems. In the process we have compiled observational aspects from the existing literature, as well as performing new analyses. We argue that during the rising phase of a black hole transient outburst the steady jet known to be associated with the canonical ‘low/hard’ state persists while the X-ray spectrum initially softens. Subsequently, the jet becomes unstable and an optically thin radio outburst is always associated with the soft X-ray peak at the end of this phase of softening. This peak corresponds to a ‘soft very high state’ or ‘steep power-law’ state. Softer X-ray states are not associated with ‘core’ radio emission. We further demonstrate quantitatively that the transient jets associated with these optically thin events are considerably more relativistic than those in the ‘low/hard’ X-ray state. This in turn implies that, as the disc makes its collapse inwards, the jet Lorentz factor rapidly increases, resulting in an internal shock in the outflow, which is the cause of the observed optically thin radio emission. We provide simple estimates for the efficiency of such a shock in the collision of a fast jet with a previously generated outflow that is only mildly relativistic. In addition, we estimate the jet power for a number of such transient events as a function of X-ray luminosity, and find them to be comparable to an extrapolation of the functions estimated for the ‘low/hard’ state jets. The normalization may be larger, however, which may suggest a contribution from some other power source such as black hole spin, for the transient jets. Finally, we attempt to fit these results together into a coherent semiquantitative model for the disc–jet coupling in all black hole X-ray binary systems.

We report on a consistent and comprehensive spectral analysis of the X-ray emission of 25 black hole X-ray binaries.All publicly available observations of the black hole binaries in the RXTE archive were analysed.Three different types of model were fitted to investigate the spectral changes occurring during an outburst.For the population, as well as for each binary and each outburst from each binary, we construct two diagnostic diagrams.The hardness intensity/luminosity diagram (HID/HLD), the X-ray colour against the flux/luminosity of the binary, is most useful when studying a single binary.However, to compare different binary systems, the disc fraction luminosity diagram (DFLD) is more useful.The DFLD uses the luminosities of the disc and power-law components to calculate the ratio of the disc luminosity to the total luminosity, resulting in a more physical value, which is analogous to the X-ray colour calculated for X-ray binaries.The tracks of the outbursts populate the DFLD more evenly than the HLD.We discuss the limitations of both diagnostic diagrams for the study of the X-ray binary outbursts and clearly illustrate how the two diagrams map on to each other for real outburst data.The similarity of the X-ray colour and disc fraction behaviour over time during an outburst originally seen in GX 339-4 data is seen in other sources' outbursts.We extract the peak luminosities in a single outburst, as well as the luminosities at the transitions away from and returning to the power-law-dominated state for each outburst.The distribution of the luminosities at the transition from the power-law to the disc-dominated state peaks at around 0.3L Edd , the same as the peak of the distribution of the peak luminosities in an outburst.Using the disc fraction to calculate the transition luminosities shows that the distributions of the luminosities for the transitions away from and returning to the power-law-dominated state are both broad and appear to overlap.Using the change in disc fraction to calculate the date when a transition occurred is not drastically different from obtaining the dates from changes in the timing behaviour of the X-ray binary.In addition, we calculate the rate of motion of an X-ray binary through the DFLD during an outburst, a diagnostic which has the potential to be used as a comparison with populations of active galactic nuclei.The fastest rate of motion is on the egress and ingress from the power-law-dominated state.A further region of increased speed through the diagram occurs in the disc-dominated state on the return to the power-lawdominated state.Finally, we compare the measured X-ray luminosities with a small number of contemporaneous radio measurements.Overall, this is the most comprehensive and uniform global study of black hole X-ray binaries to date.

We show that the model proposed by Esin, McClintock, & Narayan for the low state, intermediate state, and high state of the black hole soft X-ray transient, Nova Muscae 1991, is consistent with the spectral evolution of the black hole X-ray binary, Cyg X-1, during the hard-to-soft state transition observed in 1996. We also apply the model to the outbursts of two other black hole X-ray transients, GRO J0422+32 and GRO J1719-24.

We present results from spectral modeling of three black hole X-ray binaries: LMC X-3, GRO J1655-40, and XTE J1550-564. Using a sample of disk-dominated observations, we fit the data with a range of spectral models that includes a simple multitemperature blackbody (DISKBB), a relativistic accretion disk model based on color-corrected blackbodies (KERRBB), and a relativistic model based on non-LTE atmosphere models within an α prescription (BHSPEC). BHSPEC provides the best fit for a BeppoSAX observation of LMC X-3, which has the broadest energy coverage of our sample. It also provides the best fit for multiple epochs of Rossi X-Ray Timing Explorer ( RXTE ) data in this source, except at the very highest luminosity ( L / L Edd ≳ 0.7), where additional physics must be coming into play. BHSPEC is also the best-fit model for multiepoch RXTE observations of GRO J1655-40 and XTE J1550-564, although the best-fit inclination of the inner disk differs from the binary inclination. All our fits prefer α = 0.01 to α = 0.1, in apparent disagreement with the large stresses inferred from the rapid rise times observed in outbursts of these two sources. In all three sources our fits imply moderate black hole spins ( a * ~ 0.1-0.8), but this is sensitive to the reliability of independent measurements of these system parameters and to the physical assumptions that underly our spectral models.

Four persistent (Cygnus X-1, GX 339−4, GRS 1758−258 and 1E 1740.7−2942) and three transient (GS 2023+38, GRO J0422+32 and GS 1354−64) black hole X-ray binary systems have been extensively observed at radio wavelengths during extended periods in the low/hard X-ray state, which is characterized in X-rays by a hard power-law spectrum and strong variability. All seven systems show a persistent flat or inverted (in the sense that α≳0, where S∝να) radio spectrum in this state, markedly different from the optically thin radio spectra exhibited by most X-ray transients within days of outburst. Furthermore, in none of the systems is a high-frequency cut-off to this spectral component detected, and there is evidence that it extends to near-infrared or optical regimes. Luminous persistent hard X-ray states in the black hole system GRS 1915+105 produce a comparable spectrum. This spectral component is considered to arise in synchrotron emission from a conical, partially self-absorbed jet, of the same genre as those originally considered for active galactic nuclei. Whatever the physical origin of the low/hard X-ray states, these self-similar outflows are an ever-present feature. The power in the jet component is likely to be a significant () and approximately fixed fraction of the total accretion luminosity. The correlation between hard X-ray and synchrotron emission in all the sources implies that the jets are intimately related to the Comptonization process, and do not have very large bulk Lorentz factors, unless the hard X-ray emission is also beamed by the same factor.

In X-ray binaries, compact jets are known to commonly radiate at radio to infrared frequencies, whereas at optical to γ-ray energies, the contribution of the jet is debated. The total luminosity, and hence power of the jet, is critically dependent on the position of the break in its spectrum, between optically thick (self-absorbed) and optically thin synchrotron emission. This break, or turnover, has been reported in just one black hole X-ray binary (BHXB) thus far, GX 339−4, and inferred via spectral fitting in two others, A0620−00 and Cyg X−1. Here, we collect a wealth of multi-wavelength data from the outbursts of BHXBs during hard X-ray states, in order to search for jet breaks as yet unidentified in their spectral energy distributions. In particular, we report the direct detection of the jet break in the spectrum of V404 Cyg during its 1989 outburst, at νb = (1.8 ± 0.3) × 1014 Hz (1.7 ± 0.2 μm). We increase the number of BHXBs with measured jet breaks from three to eight. Jet breaks are found at frequencies spanning more than two orders of magnitude, from νb = (4.5 ± 0.8) × 1012 Hz for XTE J1118+480 during its 2005 outburst, to νb > 4.7 × 1014 Hz for V4641 Sgr in outburst. A positive correlation between jet break frequency and luminosity is expected theoretically; νb∝L∼ 0.5ν, jet if other parameters are constant. With constraints on the jet break in a total of 12 BHXBs including two quiescent systems, we find a large range of jet break frequencies at similar luminosities and no obvious global relation (but such a relation cannot be ruled out for individual sources). We speculate that different magnetic field strengths and/or different radii of the acceleration zone in the inner regions of the jet are likely to be responsible for the observed scatter between sources. There is evidence that the high-energy cooling break in the jet spectrum shifts from UV energies at LX ∼ 10−8LEdd (implying the jet may dominate the X-ray emission in quiescence) to X-ray energies at ∼10−3LEdd. Finally, we find that the jet break luminosity scales as Lν, jet∝L0.56 ± 0.05X (very similar to the radio–X-ray correlation), and radio-faint BHXBs have fainter jet breaks. In quiescence the jet break luminosity exceeds the X-ray luminosity.

We present a new picture for the central regions of Black Hole X-ray Binaries. In our view, these central regions have a multi-flow configuration which consists in (1) an outer standard accretion disc down to a transition radius rJ; (2) an inner magnetized accretion disc below rJ driving (3) a non relativistic self-collimated electron-proton jet surrounding, when adequate conditions for pair creation are met; (4) a ultra relativistic electron-positron beam. This accretion-ejection paradigm provides a simple explanation to the canonical spectral states, from radio to X/γ-rays, by varying the transition radius rJ and disc accretion rate independently. Large values of rJ correspond to the Quiescent state for low and the Hard state for larger . These states are characterized by the presence of a steady electron-proton MHD jet emitted by the disc below rJ. The hard X-ray component is expected to form at the jet basis. When rI becomes smaller than the marginally stable orbit ri, the whole disc resembles a standard accretion disc with no jet, characteristic of the Soft state. Intermediate states correspond to situations where . At large , an unsteady pair cascade process is triggered within the jet axis, giving birth to flares and ejection of relativistic pair blobs. This would correspond to the luminous intermediate state, sometimes referred to as the Very High state, with its associated superluminal motions. The variation of rJ independently of is a necessary ingredient in this picture. It arises from the presence of a large scale vertical magnetic field threading the disc. Features such as possible hysteresis and the presence of quasi-periodic oscillations would naturally fit within this new framework.

We investigate the dependence of observational properties of black hole X-ray binaries on the inclination angle i of their orbits. We find the following: (1) Transient black hole binaries show no trend in their quiescent X-ray luminosities as a function of i , suggesting that the radiation is not significantly beamed. This is consistent with emission from an accretion disk. If the X-rays are from a jet, then the Lorentz factor γ of the jet is <1.24 at the 90% confidence level. (2) The X-ray binary 4U 1543-47 with i ~ 21° has a surprisingly strong fluorescent iron line in the high soft state. Quantifying an earlier argument by Park et al., we conclude that if the continuum X-ray emission in this source is from a jet, then γ < 1.04. (3) None of the known binaries has cos i < 0.25 or i > 75°. This fact, plus the lack of eclipses among the 20 black hole binaries in our sample, strongly suggests at the 99.5% confidence level that systems with large inclination angles are hidden from view. The obscuration could be the result of disk flaring, as suggested by Milgrom for neutron star X-ray binaries. (4) Transient black hole binaries with i ~ 70°-75° have significantly more complex X-ray light curves than systems with i ≲ 65°. This may be the result of variable obscuration and/or variable height above the disk of the radiating gas.

ABSTRACT Using the Very Long Baseline Array and the European Very Long Baseline Interferometry Network, we have made a precise measurement of the radio parallax of the black hole X-ray binary MAXI J1820+070, providing a model-independent distance to the source. Our parallax measurement of (0.348 ± 0.033) mas for MAXI J1820+070 translates to a distance of (2.96 ± 0.33) kpc. This distance implies that the source reached (15 ± 3) per cent of the Eddington luminosity at the peak of its outburst. Further, we use this distance to refine previous estimates of the jet inclination angle, jet velocity, and the mass of the black hole in MAXI J1820+070 to be (63 ± 3)°, (0.89 ± 0.09) c, and (9.2 ± 1.3) M⊙, respectively.

We report on deep, coordinated radio and X-ray observations of the black hole X-ray binary XTE J1118+480 in quiescence. The source was observed with the Karl G. Jansky Very Large Array for a total of 17.5 h at 5.3 GHz, yielding a 4.8 ± 1.4 μJy radio source at a position consistent with the binary system. At a distance of 1.7 kpc, this corresponds to an integrated radio luminosity between 4 and 8 × 1025 erg s−1, depending on the spectral index. This is the lowest radio luminosity measured for any accreting black hole to date. Simultaneous observations with the Chandra X-ray Telescope detected XTE J1118+480 at 1.2 × 10−14 erg s−1 cm−2 (1–10 keV), corresponding to an Eddington ratio of ∼4 × 10−9 for a 7.5 M⊙ black hole. Combining these new measurements with data from the 2005 and 2000 outbursts available in the literature, we find evidence for a relationship of the form ℓr = α+βℓX (where ℓ denotes logarithmic luminosities), with β = 0.72 ± 0.09. XTE J1118+480 is thus the third system – together with GX339-4 and V404 Cyg – for which a tight, non-linear radio/X-ray correlation has been reported over more than 5 dex in ℓX. Confirming previous results, we find no evidence for a dependence of the correlation normalization of an individual system on orbital parameters, relativistic boosting, reported black hole spin and/or black hole mass. We then perform a clustering and linear regression analysis on what is arguably the most up-to-date collection of coordinated radio and X-ray luminosity measurements from quiescent and hard-state black hole X-ray binaries, including 24 systems. At variance with previous results, a two-cluster description is statistically preferred only for random errors ≲0.3 dex in both ℓr and ℓX, a level which we argue can be easily reached when the known spectral shape/distance uncertainties and intrinsic variability are accounted for. A linear regression analysis performed on the whole data set returns a best-fitting slope β = 0.61 ± 0.03 and intrinsic scatter σ0 = 0.31 ± 0.03 dex.