INTEGRAL IBIS/ISGRI energy calibration in OSA 10

We present the new energy calibration of the ISGRI detector onboard INTEGRAL, that has been implemented in the Offline Scientific Analysis (OSA) version 10. With the previous OSA 9 version, a clear departure from stability of both W and 22Na background lines was observed after MJD 54307 (revolution ~583). To solve this problem, the energy correction in OSA 10 uses: 1) a new description for the gain depending on the time and the pulse rise time, 2) an improved temperature correction per module, and 3) a varying shape of the low threshold, corrected for the change in energy resolution. With OSA 10, both background lines show a remarkably stable behavior with a relative energy variation below 1% around the nominal position (>6% in OSA 9), and the energy reconstruction at low energies is more stable compared to previous O

Gamma-ray emitting radio galaxies at hard X-rays: Seyfert core or jet emission?

A number of radio galaxies has been detected by Fermi/LAT in the gamma-ray domain. In some cases, like Cen A and M 87, these objects have been seen even in the TeV range by Cherenkov telescopes. Whereas the gamma-ray emission is likely to be connected with the non-thermal jet emission, dominating also the radio band, the situation is less clear at hard X-rays. While the smoothly curved continuum emission and the overall spectral energy distribution indicate a non-thermal emission, other features such as the iron line emission and the low variability appear to be rather of Seyfert type, i.e. created in the accretion disk and corona around the central black hole. We investigate several prominent cases using combined X-ray and gamma-ray data in order to constrain the possible contributions of the jet and the accretion disk to the overall spectral energy distribution in radio galaxies. Among the three sources we study, three different origins of the hard X-ray flux can be identified. The emission can be purely non-thermal and caused by the jet, as in the case of M 87, or thermal inverse Compton emission from the Seyfert type core (Cen A), or appears to be a superposition of non-thermal and thermal inverse Compton emission, as we observe in 3C 111. Gamma-ray bright radio galaxies host all kinds of AGN cores, Seyfert 1 and 2, BL Lac objects, and also LINER.

The nature of the multi-wavelength emission of 3C 111

We attempt to determine the nature of the high energy emission of the radio galaxy 3C 111, by distinguishing between the effects of the thermal and non-thermal processes. We study the X-ray spectrum of 3C 111 between 0.4 keV and 200 keV, and its spectral energy distribution, using data from the Suzaku satellite combined with INTEGRAL, Swift/BAT data, and Fermi/LAT data. We then model the overall spectral energy distribution including radio and infrared data. The combined Suzaku, Swift and INTEGRAL data are represented by an absorbed exponentially cut-off power-law with reflection from neutral material with a photon index Gamma = 1.68+-0.03, a high-energy cut-off Ecut = 227+143-67 keV, a reflection component with R = 0.7+-0.3 and a Gaussian component to account for the iron emission-line at 6.4 keV with an equivalent width of EW = 85+-11 eV. The X-ray spectrum appears dominated by thermal, Seyfert-like processes, but there are also indications of non-thermal processes. The radio to gamma-ray spectral energy distribution can be fit with a single-zone synchrotron-self Compton model, with no need for an additional thermal component. We suggest a hybrid scenario to explain the broad-band emission, including a thermal component (iron line, reflection) that dominates in the X-ray regime and a non-thermal one to explain the spectral energy distribution.