We report on the identification of a new γ-ray-emitting narrow-line Seyfert 1 (NLS1) galaxy, SDSS J122222.55+041315.7, which increases the number of known objects of this remarkable but rare type of active galactic nuclei (AGN) to seven. Its optical spectrum, obtained in the Sloan Digital Sky Survey-Baryon Oscillation Spectroscopic Survey, reveals a broad H β emission line with a width (FWHM) of 1734±104 km s −1 . This, along with strong optical Fe II multiplets [R 4570 = 0.9] and a weak [O III] λ 5007 emission line, makes the object a typical NLS1. On the other hand, the source exhibits a high radio brightness temperature, rapid infrared variability, and a flat X-ray spectrum extending up to ∼200 keV. It is associated with a luminous γ-ray source detected significantly with Fermi/LAT. Correlated variability with other wavebands has not yet been tested. The spectral energy distribution can be well modelled by a one-zone leptonic jet model. This new member is by far the most distant γ-rayemitting NLS1, at a redshift of z = 0.966.
The truncation of an optically thick, geometrically thin accretion disk is investigated in the context of low-luminosity AGNs (LLAGNs). We generalize the disk evaporation model used in the interpretative framework of black hole X-ray binaries by including the effect of a magnetic field in accretion disks surrounding supermassive black holes. The critical transition mass accretion rate for which the disk is truncated is found to be insensitive to magnetic effects, but its inclusion leads to a smaller truncation radius in comparison to a model without its consideration. That is, a thin viscous disk is truncated for LLAGNs at an Eddington ratio less than 0.03 for a standard viscosity parameter (α = 0.3). An increase of the viscosity parameter results in a higher critical transition mass accretion rate and a correspondingly smaller truncation distance, the latter accentuated by greater magnetic energy densities in the disk. Based on these results, the truncation radii inferred from spectral fits of LLAGNs published in the literature are consistent with the disk evaporation model. The infrared emission arising from the truncated geometrically thin accretion disks may be responsible for the red bump seen in such LLAGNs.
Observations show that there is a positive correlation between Eddington ratio λ and hard X-ray index Γ for λ 0.01, and there is an anti-correlation between λ and Γ for λ 0.01 in black hole X-ray binaries (with λ = L bol /L Edd ). In this work, we theoretically investigate the correlation between Γ and λ within the framework of disk-corona model. We improve the model by taking into account all cooling processes including synchrotron and self-Compton radiations in the corona, Comptonization of the soft photons from the underlying accretion disk, and the Bremsstrahlung radiations. Presuming that the coronal flow above the disk can reach up to 0.1 Eddington rate at the outer region, we calculate the structure of the two-phase accretion flows and the emergent spectra for accretion rates from 0.003 to 0.1. It is found that at accretion rates larger than ∽ 0.01 Eddington rate a fraction of coronal gas condenses into the disk and an inner disk can be sustained by condensation. In this case, the X-ray emission is dominated by the scattering the soft photon from the underlying disk in the corona. The emission from the inner disk and corona can produce the positive correlation between λ and Γ. While at accretion rates lower than ∽ 0.01 Eddington accretion rate, the inner disk vanishes completely by evaporation, the accretion is dominated by ADAF, in which the X-ray emission is produced by the Comptonization of the synchrotron and bremsstrahlung photons of ADAF itself. The emission from ADAF can produce the anti-correlation between λ and Γ. We show that our model can roughly explain the observed evolution of Γ 3−25keV with L 0.5−25keV /L Edd for the black hole X-ray transient H1743-322 in the decay of 2003 from thermal dominated state to low/hard state.
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