Long‐Term Monitoring of NGC 4151 by OSSE

Johnson, W. N.; McNaron-Brown, K.; Kurfess, J. D.; Zdziarski, A. A.; Magdziarz, P.; Gehrels, N.

doi:10.1086/304148

Cited by 45 publications

(42 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We find that the form of the high-energy cutoff is almost the same in both sources, as shown in Fig. 9, which shows the ratio of the OSSE spectrum of GX 339-4 (from the entire observation of 1991 September 5-12) to the spectrum of NGC 4151 averaged over all OSSE observations (from Johnson et al 1997). …”

Section: Seyfert 1smentioning

confidence: 62%

“…On the other hand, it is also possible that nonthermal acceleration of selected electrons to relativistic energies operates in the source in addition to heating of the plasma. This hybrid model has been applied to NGC 4151 by Zdziarski et al (1996) and Johnson et al (1997) and to Cyg X-1 by Poutanen & Coppi (1998) and Poutanen (1998). We have applied that model to the data set 1.…”

Section: E ± Pair Productionmentioning

confidence: 99%

See 1 more Smart Citation

Broad-band X-ray/γ-ray spectra and binary parameters of GX 339–4 and their astrophysical implications

Zdziarski¹,

Poutanen²,

Mikołajewska³

et al. 1998

Monthly Notices of the Royal Astronomical Society

195

217

View full text Add to dashboard Cite

We present X-ray/γ-ray spectra of the binary GX 339-4 observed in the hard state simultaneously by Ginga and CGRO OSSE during an outburst in 1991 September. The Ginga X-ray spectra are well represented by a power law with a photon spectral index of Γ ≃ 1.75 and a Compton reflection component with a fluorescent Fe Kα line corresponding to a solid angle of an optically-thick, ionized, medium of ∼ 0.4×2π. The OSSE data ( 50 keV) require a sharp high-energy cutoff in the power-law spectrum. The broad-band spectra are very well modelled by repeated Compton scattering in a thermal plasma with an optical depth of τ ∼ 1 and kT ≃ 50 keV. We also study the distance to the system and find it to be > ∼ 3 kpc, ruling out earlier determinations of ∼ 1 kpc. Using this limit, the observed reddening and the orbital period, we find the allowed range of the mass of the primary is consistent with it being a black hole.We find the data are incosistent with models of either homogenous or patchy coronae above the surface of an accretion disc. Rather, they are consistent with the presence of a hot inner hot disc with the viscosity parameter of α ∼ 1 accreting at a rate close to the maximum set by advection. The hot disc is surrounded by a cold outer disc, which gives rise to the reflection component and a soft X-ray excess, also present in the data. The seed photons for Comptonization are unlikely to be due to thermal synchrotron radiation. Rather, they are supplied by the outer cold disc and/or cold clouds within the hot disc. e ± pair production is negligible if electrons are thermal. The hot disc model, which scaled parameters are independent of the blackhole mass, is supported by the similarity of the spectrum of GX 339-4 to those of other black-hole binaries and Seyfert 1s. On the other hand, their spectra in the soft γ-ray regime are significantly harder than those of weakly-magnetized neutron stars. Based on this difference, we propose that the presence of broad-band spectra corresponding to thermal Comptonization with kT > ∼ 50 keV represents a black-hole signature.

show abstract

Section: Seyfert 1smentioning

confidence: 62%

Section: E ± Pair Productionmentioning

confidence: 99%

Broad-band X-ray/γ-ray spectra and binary parameters of GX 339–4 and their astrophysical implications

Zdziarski¹,

Poutanen²,

Mikołajewska³

et al. 1998

Monthly Notices of the Royal Astronomical Society

195

217

View full text Add to dashboard Cite

show abstract

“…Yaqoob et al (1993) also note that the spectral slope changes occur on roughly the same time‐scale as the flux variations. However, a perplexing aspect of the spectral index flux correlation observed in the medium energy bandpass is that the effect is not mirrored in the hard X‐ray/soft gamma regime (Johnson et al 1997; Piro et al 2002).…”

Section: Discussionmentioning

confidence: 99%

Characterizing the complex absorber in NGC 4151

Schurch¹,

Warwick²

2002

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We present a detailed analysis of the complex absorption apparent in the 2–6 keV X‐ray spectrum of the bright nearby Seyfert galaxy NGC 4151. We first utilize the large bandpass and medium spectral resolution afforded by BeppoSAX data to construct a 1–100 keV spectral template, which assumes the absorption arises in both warm (i.e. partially photoionized) and cold gas present in the line of sight to the active nucleus of the source. Application of this spectral model to an ASCA‘long‐look’ observation of NGC 4151 reveals a partial correlation between the underlying continuum flux and the ionization state of the warm absorber. Such a correlation is an intrinsic property of a warm absorber and argues strongly in favour of this interpretation for the complex absorbing column over alternative partial covering models. The warm absorber in NGC 4151 has a column density of ∼2 × 1023 cm −2, with an ionization parameter in the range log(ξ) ≈ 2.4–2.7. The inferred relatively low density (∼105 cm−3) for the warm gas implies an equilibration time‐scale for the dominant ions of the same order as or longer than the time‐scale of the continuum variability. It follows that the warm component will invariably be observed in a non‐equilibrium ionization state. The warm absorber in NGC 4151 may be identified as a multi‐temperature wind produced by evaporation from the inner edge of an obscuring torus as discussed in a recent paper by Krolik & Kriss. The unusually complex character of the absorption seen in NGC 4151 may then be explained in terms of a fortuitous line of sight which grazes the top edge of the obscuring torus so as to intercept a substantial column of both the warm and cold gas. We also find that (i) the reported hardening of the spectrum of NGC 4151 as the continuum level falls may be simply due to the presence of an underlying (hard and relatively constant) Compton‐reflection component, and (ii) the iron Kα line has a relatively narrow Gaussian profile and a line flux that remains constant over both short (days) and long (months to years) time‐scales–a relativistically broadened iron Kα feature was not required in our modelling.

show abstract

“…The energy spectra of AGNs and stellar mass black holes in X-ray binaries often exhibit evidence for the presence of such a component (see Inoue & Doi 2014;Johnson et al 1997;Coppi 2003;Malzac & Belmont 2009, and references therein). We assume that the energy spectrum of the thermal electron component is described by the Maxwell-Juttner distribution:…”

Section: Non-thermal Plasmamentioning

confidence: 99%

The X-Ray Polarization of the Accretion Disk Coronae of Active Galactic Nuclei

Beheshtipour

Krawczynski

Malzac

2017

ApJ

View full text Add to dashboard Cite

Hard X-rays observed in Active Galactic Nuclei (AGNs) are thought to originate from the Comptonization of the optical/UV accretion disk photons in a hot corona. Polarization studies of these photons can help to constrain the corona geometry and the plasma properties. We have developed a ray-tracing code that simulates the Comptonization of accretion disk photons in coronae of arbitrary shape, and use it here to study the polarization of the X-ray emission from wedge and spherical coronae. We study the predicted polarization signatures for the fully relativistic and various approximate treatments of the elemental Compton scattering processes. We furthermore use the code to evaluate the impact of nonthermal electrons and cyclo-synchrotron photons on the polarization properties. Finally, we model the NuSTAR observations of the Seyfert I galaxy Mrk 335 and predict the associated polarization signal. Our studies show that X-ray polarimetry missions such as NASA's Imaging X-ray Polarimetry Explorer (IXPE) and the X-ray Imaging Polarimetry Explorer (XIPE) proposed to ESA will provide valuable new information about the physical properties of the plasma close to the event horizon of AGN black holes.

show abstract

Long‐Term Monitoring of NGC 4151 by OSSE

Cited by 45 publications

References 24 publications

Broad-band X-ray/γ-ray spectra and binary parameters of GX 339–4 and their astrophysical implications

Broad-band X-ray/γ-ray spectra and binary parameters of GX 339–4 and their astrophysical implications

Characterizing the complex absorber in NGC 4151

The X-Ray Polarization of the Accretion Disk Coronae of Active Galactic Nuclei

Contact Info

Product

Resources

About