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تسجيل مستخدم جديدDiscovery of ultra-fast outflows in a sample of Broad Line Radio Galaxies observed with Suzaku
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We present the results of a uniform and systematic search for blue-shifted Fe K absorption lines in the X-ray spectra of five bright Broad-Line Radio Galaxies (BLRGs) observed with Suzaku. We detect, for the first time at X-rays in radio-loud AGN, several absorption lines at energies greater than 7 keV in three out of five sources, namely 3C 111, 3C 120 and 3C 390.3. The lines are detected with high significance according to both the F-test and extensive Monte Carlo simulations. Their likely interpretation as blue-shifted Fe XXV and Fe XXVI K-shell resonance lines implies an origin from highly ionized gas outflowing with mildly relativistic velocities, in the range 0.04-0.15c. A fit with specific photo-ionization models gives ionization parameters in the range log_xi~4-5.6 and column densities of N_H~10^22-10^23 cm^-2. These characteristics are very similar to those of the Ultra-Fast Outflows (UFOs) previously observed in radio-quiet AGN. Their estimated location within ~0.01-0.3pc from the central super-massive black hole suggests a likely origin related with accretion disk winds/outflows. Depending on the absorber covering fraction, the mass outflow rate of these UFOs can be comparable to the accretion rate and their kinetic power can correspond to a significant fraction of the bolometric luminosity and is comparable to their typical jet power. Therefore, these UFOs can play a significant role in the expected feedback from the AGN on the surrounding environment and can give us further clues on the relation between the accretion disk and the formation of winds/jets in both radio-quiet and radio-loud AGN.
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The study of winds in active galactic nuclei (AGN) is of utmost importance as they may provide the long sought-after link between the central black hole and the host galaxy, establishing the AGN feedback. Recently, Laha et al. (2014) reported the X-r
ay analysis of a sample of 26 Seyferts observed with XMM-Newton, which are part of the so-called warm absorbers in X-rays (WAX) sample. They claim the non-detection of Fe K absorbers indicative of ultra-fast outflows (UFOs) in four observations previously analyzed by Tombesi et al. (2010). They mainly impute the Tombesi et al. detections to an improper modeling of the underlying continuum in the E=4-10 keV band. We therefore re-address here the robustness of these detections and we find that the main reason for the claimed non-detections is likely due to their use of single events only spectra, which reduces the total counts by 40%. Performing a re-analysis of the data in the whole E=0.3-10 keV energy band using their models and spectra including also double events, we find that the blue-shifted Fe K absorption lines are indeed detected at >99%. This work demonstrates the robustness of these detections in XMM-Newton even including complex model components such as reflection, relativistic lines and warm absorbers.
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n energy range; a detailed look at the temporal characteristics of the observed gamma-ray emission reveals in addition possible flux variability in both sources. No statistically significant gamma-ray detection of the other BLRGs was however found in the considered dataset. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in gamma-rays is the particularly strong nuclear radio flux. This finding, together with the indications of the gamma-ray flux variability and a number of other arguments presented, indicate that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets observed at intermediate viewing angles. In this paper we also analyzed a comparison sample of high accretion-rate Seyfert 1 galaxies, which can be considered radio-quiet counterparts of BLRGs, and found none were detected in gamma-rays. A simple phenomenological hybrid model applied for the broad-band emission of the discussed radio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to the accreting matter is > 1 percent on average for BLRGs, whilst <0.1 percent for Seyfert 1 galaxies.
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