The spectrum of the cosmic X-ray background observed by RTXE/PCA

Free access article

Issue		A&A Volume 411, Number 3, December I 2003


Page(s)		329 - 334
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20031386

A&A 411, 329-334 (2003)
DOI: 10.1051/0004-6361:20031386

The spectrum of the cosmic X-ray background observed by RTXE/PCA

M. Revnivtsev^{1, 2}, M. Gilfanov^{1, 2}, R. Sunyaev^{1, 2}, K. Jahoda³ and C. Markwardt³

¹ Max-Planck-Institute für Astrophysik, Karl-Schwarzschild-Str. 1, 85740 Garching bei München, Germany
² Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, 117810 Moscow, Russia
³ Laboratory for High Energy Astrophysics, Code 662, Goddard Space Flight Center, Greenbelt, MD 20771, USA

(Received 24 June 2003 / Accepted 29 August 2003 )

Abstract
We have analyzed a large set of RXTE/PCA scanning and slewing observations performed between April 1996 and March 1999. We obtained the 3-20 keV spectrum of the cosmic X-ray background (CXB) by subtracting Earth-occulted observations from observations of the X-ray sky at high galactic latitude and far away from sources. The sky coverage is approximately ~ $22.6\times 10^{3}$ deg ². The PCA spectrum of CXB in 3-20 keV energy band is adequately approximated by a single power law with photon index $\Gamma\sim 1.4$ and normalization at 1 keV $\sim9.5$ phot/s/cm ²/keV/sr. Instrumental background uncertainty precludes accurate RXTE/PCA measurements of the spectrum of cosmic X-ray background at energies above 15 keV and therefore we cannot detect the high energy cutoff observed by the HEAO-1 A2 experiment. Deep observations of the 6 high latitude points used to model the PCA background provide a coarse measure of the spatial variation of the CXB. The CXB variations are consistent with a fixed spectral shape and variable normalization characterized by a fractional rms amplitude of ~7% on angular scales of ~1 square deg.

Key words: cosmology: observations -- diffuse radiation -- X-rays: general

Offprint request: M. Revnivtsev, mikej@mpa-garching.mpg.de

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