OSSE Observations of Gamma-Ray Emission from Centaurus A

Kinzer, R. L.; Johnson, W. N.; Dermer, C. D.; Kurfess, J. D.; Strickman, M. S.; Grove, J. E.; Kroeger, R. A.; Grabelsky, D. A.; Purcell, W. R.; Ulmer, M. P.; Jung, G. V.; McNaron-Brown, K.

doi:10.1086/176036

Cited by 82 publications

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“…In this period, this source exhibited X-ray variability (Bond et al 1996) and also some soft γ-ray variability (Bond et al 1996;Kinzer et al 1995;Steinle et al 1998). However, Sreekumar et al (1999) found that the EGRET flux was stable during the whole period of CGRO observations.…”

Section: Cen Amentioning

confidence: 93%

A lepto-hadronic model for high-energy emission from FR I radiogalaxies

Reynoso

Medina

Romero

2011

A&A

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Context. The well known radiogalaxy Cen A has been recently detected as a source of very high energy (VHE) γ-rays by the HESS experiment just before Fermi/LAT detected it at high energies (HE). The detection, together with that of M 87, established radiogalaxies as VHE γ-ray emitters. Aims. The aim of this work is to present a lepto-hadronic model for the VHE emission from the relativistic jets in FR I radiogalaxies. Methods. We consider that protons and electrons are accelerated in a compact region near the base of the jet, and they cool emitting multi wavelength radiation as propagating along the jet. The proton and electron distributions are obtained through steady-state transport equation taking into account acceleration, radiative and non-radiative cooling processes, as well as particle transport by convection. Results. Considering the effects of photon absorption at different wavelengths, we calculate the radiation emitted by the primary protons and electrons, as well as the contribution of secondaries particles (e ± , πs and μs). The expected high-energy neutrino signal is also obtained and the possibility of detections with KM3NeT and IceCube is discussed. Conclusions. The spectral energy distribution obtained in our model with an appropriate set of parameters for an extended emission zone can account for much of the observed spectra for both AGNs.

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Section: Cen Amentioning

confidence: 93%

A lepto-hadronic model for high-energy emission from FR I radiogalaxies

Reynoso

Medina

Romero

2011

A&A

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“…The value of the folding energy of CenA is discussed extensively in the literature, with no clear consensus. For example, Rothschild et al (2006) measure a folding energy 1.5 MeV > using RXTE while at a similar luminosity, Kinzer et al (1995) find E 254 33 keV cut =  using CGRO/OSSE data. From the fluxes and spectral shape measured between 0.2 and 30 GeV with Fermi it is clear that the spectrum needs to roll over or break somewhere in the 100-1000 keV range (Abdo et al 2010b).…”

Section: Spectral Curvature At High Energiesmentioning

confidence: 99%

“…As discussed above, this effect is likely connected to the difference between a cutoffpl and a realistic Comptonization model: the cutoffpl model is constantly curving, even far below the folding energy, while a realistic Compton spectrum is much more power-law-like at energies significantly below the temperature of the Comptonization plasma and rolls over more steeply than the cutoffpl above it (see Figure 3 in Fabian et al 2015 and references therein). γ-ray instruments like INTEGRAL therefore detect the cutoff, but given their typically lower statistics at soft X-rays find an acceptable solution with a cutoffpl or a broken power-law model (Kinzer et al 1995;Beckmann et al 2011). For the X-ray instruments, on the other hand, the rollover is outside their energy range and they mainly measure the power-law part of the Comptonization spectrum, resulting in unconstrained or very high folding energies when using cutoffpl.…”

Section: Spectral Curvature At High Energiesmentioning

confidence: 99%

“…If the flux variability were induced by the inner jet component, we would expect some influence on the hard X-ray continuum. On the other hand, variability of the cutoff-energy as a function of flux has been observed with soft γ-ray instruments (e.g., with CGRO, Kinzer et al 1995), following the "softer-when-brighter" correlation of Seyfert galaxies.…”

Section: The Geometry and Physics Of The X-ray Coronamentioning

confidence: 99%

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NuSTAR AND XMM-NEWTON OBSERVATIONS OF THE HARD X-RAY SPECTRUM OF CENTAURUS A

Fürst

Müller

Madsen

et al. 2016

ApJ

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We present simultaneous XMM-Newton and Nuclear Spectroscopic Telescope Array (NuSTAR) observations spanning 3-78 keV of the nearest radio galaxy, CentaurusA (Cen A). The accretion geometry around the central engine in CenA is still debated, and we investigate possible configurations using detailed X-ray spectral modeling. NuSTAR imaged the central region of CenA with subarcminute resolution at X-ray energies above 10 keV for the first time, but found no evidence for an extended source or other off-nuclear point sources. The XMM-Newton and NuSTAR spectra agree well and can be described with an absorbed power law with a photon index Γ=1.815±0.005 and a fluorescent Fe Ka line in good agreement with literature values. The spectrum does not require a high-energy exponential rollover, with a constraint of E fold >1 MeV. A thermal Comptonization continuum describes the data well, with parameters that agree with values measured by INTEGRAL, in particular an electron temperature kT e between ≈100-300 keV and seed photon input temperatures between 5 and 50 eV. We do not find evidence for reflection or a broad iron line and put stringent upper limits of R<0.01 on the reflection fraction and accretion disk illumination. We use archival Chandra data to estimate the contribution from diffuse emission, extra-nuclear point sources, and the outer X-ray jet to the observed NuSTAR and XMM-Newton X-ray spectra and find the contribution to be negligible. We discuss different scenarios for the physical origin of the observed hard X-ray spectrum and conclude that the inner disk is replaced by an advection-dominated accretion flow or that the X-rays are dominated by synchrotron self-Compton emission from the inner regions of the radio jet or a combination thereof.

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“…Adopting a power law with an exponential cutoff, the e-folding energy ranged from 300 to 700 keV depending on the brightness state of the source. The high-energy spectrum hardened with decreasing intensity (Kinzer et al 1995). Combining the data from all the CGRO instruments, OSSE, COMPTEL, and EGRET, Steinle et al (1998) showed that a further steepening of the spectrum occurs between the MeV (COMPTEL) and GeV (EGRET) energies.…”

Section: Introductionmentioning

confidence: 99%

BeppoSAXObservations of Centaurus A: The Hard Continuum and the Iron‐Line Feature

Grandi

Fiocchi²,

Perola

et al. 2003

ApJ

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The radio galaxy Centaurus A was observed by the BeppoSAX satellite five times from 1997 to 2000. From 1999 July 6 to 1999 August 17, the source was also simultaneously observed by COMPTEL on board the Compton Gamma Ray Observatory. Centaurus A has a complex spectrum with multiple extended components and a strongly absorbed (N H $ 10 23 cm À2 ) nucleus well fitted by a power law (À $ 1:8) that bends at high energies. When the BeppoSAX and COMPTEL observations are combined together, an exponential cutoff with an e-folding energy of $600 keV gives an adequate description of the spectral steepening. A complex feature in emission at 6-7 keV is resolved into two Fe K components, one narrow cold line and an ionized line centered at 6.8 keV. Significant variations have been observed in the iron feature, with the less prominent ionized line seemingly being the only one responsible for them: its variations do not appear to correlate with the strength of the continuum. The high-energy cutoff and the Fe feature suggest the presence of an accretion flow in the Centaurus A nucleus. However, the absence of a significant reflection and the narrowness of the cold line, as well as the lack of correlation between the continuum and 6.8 keV line variations, disfavor a standard cold/ionized thin disk (at least in the inner regions). A more plausible configuration might be a hot, thick, optically thin accretion flow surrounded by material with different opacities. Finally, we note that the high-energy break observed by BeppoSAX and COMPTEL could be also reasonably explained by inverse Compton radiation from a jet. If this is the case, a structured jet with outer slow layers surrounding a beamed inner region is necessary to explain the strong Fe feature observed by BeppoSAX.

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OSSE Observations of Gamma-Ray Emission from Centaurus A

Cited by 82 publications

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A lepto-hadronic model for high-energy emission from FR I radiogalaxies

A lepto-hadronic model for high-energy emission from FR I radiogalaxies

NuSTAR AND XMM-NEWTON OBSERVATIONS OF THE HARD X-RAY SPECTRUM OF CENTAURUS A

BeppoSAXObservations of Centaurus A: The Hard Continuum and the Iron‐Line Feature

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