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Despite decades of observations, the nature of the hard X-ray/soft gamma-ray emission of Cena, the brightest radio-loud AGN in the hard X-ray sky, is still unclear. The two main competing models are thermal Comptonization and synchrotron self-Compton emission. They predict a spectral cutoff of roughly 300 keV or > 1 MeV, respectively, and require spectral coverage to the MeV region to differentiate. Using archival data and observations from the current INTEGRAL AO, we investigate Cen A's spectrum using both SPI and IBIS/ISGRI to better understand the soft gamma-ray emission and the process at work in that energy range. Also, we search for spectral variability in light of recent results from Swift/BAT. We find that INTEGRAL spectra can be described by either a cutoff power law model with Ecut~550 keV or by a log parabola model.

Employing the 12 NaI detectors in the Fermi GBM, the Earth Occultation Technique (EOT) can be used to measure the fluxes of x-ray and gamma-ray sources. Each time a source passes behind the Earth (or emerges from behind the Earth), a step-like feature is produced in the detector count rate. With a predefined catalog of source positions, the times of the occultation steps can be calculated, the individual steps fit, and the fluxes derived. However, in order to find new sources and generate a complete catalog, a method is needed for generating an image of the sky. An imaging algorithm has been developed to generate all-sky images using the GBM data. Here we present imaging results from ~2.5 years of data in the 12-25 keV and 100-300 keV energy bands., Comment: 2011 Fermi Symposium proceedings - eConf C110509

The NaI and BGO detectors on the Gamma ray Burst Monitor (GBM) on Fermi are now being used for long term monitoring of the hard X-ray/low energy gamma ray sky. Using the Earth occultation technique demonstrated previously by the BATSE instrument on the Compton Gamma Ray Observatory, GBM produces multiband light curves and spectra for known sources and transient outbursts in the 8 keV - 1 MeV band with its NaI detectors and up to 40 MeV with its BGO. Coverage of the entire sky is obtained every two orbits, with sensitivity exceeding that of BATSE at energies below ~25 keV and above ~1.5 MeV. We describe the technique and present preliminary results after the first ~17 months of observations at energies above 100 keV. Seven sources are detected: the Crab, Cyg X-1, Swift J1753.5-0127, 1E 1740-29, Cen A, GRS 1915+105, and the transient source XTE J1752-223., 5 pages, 8 figures, 2009 Fermi Symposium, to be published in eConf Proceedings C091122