A New Measurement of the Cosmic X‐ray Background

Abstract

I present a new analytical description of the cosmic X‐ray background (CXRB) spectrum in the 1.5–200 keV energy band, obtained by combining the new measurement performed by the Swift X‐ray telescope (XRT) with the recently published Swift burst alert telescope (BAT) measurement. A study of the cosmic variance in the XRT band (1.5–7 keV) is also presented. I find that the expected cosmic variance (expected from LogN‐LogS) scales as Ω−0.3 (where Ω is the surveyed area) in very good agreement with XRT data.