BATSE Observations of the Piccinotti Sample of AGN
A. Malizia, L. Bassani, S.N. Zhang, A.J. Dean, W.S. Paciesas, G.G.C. Paulumbo
Abstract
BATSE Earth occultation data have been used to search for emission in the 20-100 keV band from all sources in the Piccinotti sample, which represents to date the only complete 2-10 keV survey of the extragalactic sky down to a limiting flux of 3.1 x 10^(-11) erg cm^(-2)$ s^(-1). Nearly four years of observations have been analyzed to reach a 5sigma sensitivity level of about 7.8x 10^(-11) erg cm^(-2) s^(-1) in the band considered. Of the 36 sources in the sample, 14 have been detected above 5sigma confidence level while marginal detection (3<sigma<5) can be claimed for 13 sources; for 9 objects 2sigma upper limits are reported. Comparison of BATSE results with data at higher energies is used to estimate the robustness of our data analysis: while the detection level of each source is reliable, the flux measurement maybe overestimated in some sources by as much as 35%, probably due to incomplete data cleaning. Comparison of BATSE fluxes with X-ray fluxes, obtained in the 2-10 keV range and averaged over years, indicates that a canonical power law of photon index 1.7 gives a good description of the broad band spectra of bright AGNs and that spectral breaks preferentially occur above 100 keV.