Variability and Spectral Modeling of the Hard X-Ray Emission of Gx 339–4 in a Bright Low/Hard State

Droulans, Robert; Belmont, R.; Malzac, J.; Jourdain, E.

doi:10.1088/0004-637x/717/2/1022

Cited by 45 publications

(46 citation statements)

References 57 publications

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“…In addition a high energy excess above the cut-off energy is detected in the brightest sources 3,4,5,6 (see Fig. 1).…”

Section: High Energy Emission Of Black Hole Binariesmentioning

confidence: 87%

On the Nature of the X-Ray Corona of Black Hole Binaries

Malzac

2012

Int. J. Mod. Phys. Conf. Ser.

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We discuss the nature of the X-ray emitting plasma of black hole binaries. It is well known that the temperature and optical depth of the Comptonising electrons of the X-ray corona of black hole binaries can be measured using spectroscopy in the 1 keV-1 MeV energy band. We emphasize recent developments in the modeling of high energy radiation processes which allow us to constrain other important physical parameters of the corona, such as the strength of magnetic field, or the temperature of the ions. The results appear to challenge current accretion models. In particular, standard advection dominated accretion flow do not match the observed properties of bright hard state Xray binaries such as Cygnus X-1 or GX 339-4. On the other hand, we find that all the data would be consistent with a multi-zone magnetically dominated hot accretion flow model. We also emphasize that besides the usual spectral state transitions observed at luminosities above a few percent of Eddington, there is observational evidence for at least two additional, more subtle, radiative transitions occuring at lower luminosities.Keywords: X-rays; gamma-rays; black hole physics ; accretion High energy emission of black hole binariesBlack hole binaries are observed in two main X-ray spectral states, namely the Hard State (HS) and the Soft State (SS; see Ref 1). In the HS the high energy spectrum forms a power-law with photon index Γ in the range 1.4-2 and a sharp high energy cut-of around 100 keV. These spectra are generally interpreted as thermal Comptonisation. Namely, optical, UV or soft X-ray photons are gradually up-scattered into the hard X-ray and gamma-ray domain through multiple Compton interactions with a population of hot thermal electrons of temperature T e ∼ 10 9 K. 2 Spectral fits with thermal Comptonization models allows to constrain the Thomson optical depth and temperature of the plasma. Typical parameters in the hard state are τ T ∼ 1 − 3, kT e ∼ 70 − 100 keV. It is worth stressing that in the HS the Thomson optical depth of the plasma is usually found to be larger than unity, which means that we are not dealing with an optically thin plasma. As we will see below, this has important consequences for dynamical models.In addition a high energy excess above the cut-off energy is detected in the brightest sources 3,4,5,6 (see Fig. 1). This high energy excess is generally believed to

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“…In addition a high energy excess above the cut-off energy is detected in the brightest sources 3,4,5,6 (see Fig. 1).…”

Section: High Energy Emission Of Black Hole Binariesmentioning

confidence: 87%

On the Nature of the X-Ray Corona of Black Hole Binaries

Malzac

2012

Int. J. Mod. Phys. Conf. Ser.

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“…Observational evidence of the presence of non-thermal particles in accretion flows includes detection of MeV tails (e.g., Droulans et al 2010;Zdziarski et al 2012) and patterns of optical/infrared evolution , both observed in stellar black-hole systems. However, these features are produced by nonthermal electrons, which may come from pion decay, and in principle, they do not require direct acceleration.…”

Section: Discussionmentioning

confidence: 99%

Gamma-ray activity of Seyfert galaxies and constraints on hot accretion flows

Wojaczyński

Niedźwiecki

Xie

et al. 2015

A&A

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Aims. We check how the Fermi/LAT data constrain the physics of hot accretion flows that are most likely present in low-luminosity AGNs. Methods. Using a precise model of emission from hot flows, we studied the flow γ-ray emission resulting from proton-proton interactions. We explored the dependence of the γ-ray luminosity on the accretion rate, the black hole spin, the magnetic field strength, the electron heating efficiency, and the particle distribution. Then, we compared the hadronic γ-ray luminosities predicted by the model for several nearby Seyfert 1 galaxies with the results of our analysis of 6.4 years of Fermi/LAT observations of these AGNs. Results. In agreement with previous studies, we find a significant γ-ray detection in NGC 6814. We were only able to derive upper limits for the remaining objects, although we report marginally significant (∼3σ) signals at the positions of NGC 4151 and NGC 4258. The derived upper limits for the flux above 1 GeV allow us to constrain the proton acceleration efficiency in flows with heating of electrons dominated by Coulomb interactions, which case is favored by the X-ray spectral properties. In these flows, at most ∼10% of the accretion power can be used for a relativistic acceleration of protons. Upper limits for the flux below 1 GeV can constrain the magnetic field strength and black hole spin value; we find these constraints for NGC 7213 and NGC 4151. We also note that the spectral component above ∼4 GeV previously found in the Fermi/LAT data of Centaurus A may be due to hadronic emission from a flow within the above constraint. We rule out this origin of the γ-ray emission for NGC 6814. For models with a strong magnetohydrodynamic heating of electrons, the hadronic γ-ray fluxes are below the Fermi/LAT sensitivity even for the closest AGNs. In these models, nonthermal Compton radiation may dominate in the γ-ray range if electrons are efficiently accelerated and the acceleration index is hard; for the index 2, the LAT upper limits constrain the fraction of accretion power used for such an acceleration to at most ∼5%. Finally, we note that the three Seyfert 2 galaxies with high starburst activity NGC 4595, NGC 1068, and Circinus show an interesting correlation of their γ-ray luminosities with properties of their active nuclei, and we discuss this in the context of the hot flow model.

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“…Therefore, the problem must be treated numerically Malzac & Belmont 2009;Veledina et al 2013). A comparison of modeled spectra obtained from self-consistent electron distributions against the observed spectra has been performed for the BH binaries Cyg X-1 and GX 339-4 in the X-ray/γ-ray regime Malzac & Belmont 2009;Droulans et al 2010;Del Santo et al 2013). However, simultaneous comparison with the optical/UV data has not been presented to date.…”

Section: Self-consistent Physical Modelingmentioning

confidence: 99%

The origin of seed photons for Comptonization in the black hole binary Swift J1753.5–0127

Kajava

Veledina

Tsygankov

et al. 2016

A&A

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Aims. The black hole binary Swift J1753.5-0127 is providing a unique data set to study accretion flows. Various investigations of this system and of other black holes have not, however, led to an agreement on the accretion flow geometry or on the seed photon source for Comptonization during different stages of X-ray outbursts. We place constraints on these accretion flow properties by studying long-term spectral variations of this source. Methods. We performed phenomenological and self-consistent broad band spectral modeling of Swift J1753.5-0127 using quasisimultaneous archived data from INTEGRAL/ISGRI, Swift/UVOT/XRT/BAT, RXTE/PCA/HEXTE, and MAXI/GSC instruments. Results. We identify a critical flux limit, F ∼ 1.5 × 10 −8 erg cm −2 s −1 , and show that the spectral properties of Swift J1753.5-0127 are markedly different above and below this value. Above the limit, during the outburst peak, the hot medium seems to intercept roughly 50 percent of the disk emission. Below it, in the outburst tail, the contribution of the disk photons reduces significantly and the entire spectrum from the optical to X-rays can be produced by a synchrotron-self-Compton mechanism. The long-term variations in the hard X-ray spectra are caused by erratic changes of the electron temperatures in the hot medium. Thermal Comptonization models indicate unreasonably low hot medium optical depths during the short incursions into the soft state after 2010, suggesting that non-thermal electrons produce the Comptonized tail in this state. The soft X-ray excess, likely produced by the accretion disk, shows peculiarly stable temperatures for over an order of magnitude changes in flux. Conclusions. The long-term spectral trends of Swift J1753.5-0127 are likely set by variations of the truncation radius and a formation of a hot, quasi-spherical inner flow in the vicinity of the black hole. In the late outburst stages, at fluxes below the critical limit, the source of seed photons for Comptonization is not the thermal disk, but more likely they are produced by non-thermal synchrotron emission within the hot flow near the black hole. The stability of the soft excess temperature is, however, not consistent with this picture and further investigations are needed to understand its behavior.

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Variability and Spectral Modeling of the Hard X-Ray Emission of Gx 339–4 in a Bright Low/Hard State

Cited by 45 publications

References 57 publications

On the Nature of the X-Ray Corona of Black Hole Binaries

On the Nature of the X-Ray Corona of Black Hole Binaries

Gamma-ray activity of Seyfert galaxies and constraints on hot accretion flows

The origin of seed photons for Comptonization in the black hole binary Swift J1753.5–0127

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