BATSE Observations of the Piccinotti Sample of Active Galactic Nuclei

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 the only complete 2-10 keV survey to date of the extragalactic sky down to a limiting flux of 3.1 × 10-11 ergs cm-2 s-1. Nearly 4 yr of observations have been analyzed to reach a 5 σ sensitivity level of about 7.8 × 10-11 ergs cm-2 s-1 in the band considered. Of the 36 sources in the sample, 14 have been detected above the 5 σ confidence level, while marginal detection (3 ≤ σ ≤ 5) can be claimed for 13 sources; for nine objects 2 σ upper limits are reported. A 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 because of 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 broadband spectra of bright active galactic nuclei (AGNs) and that spectral breaks preferentially occur above 100 keV.