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Astron. Astrophys. 349, L73-L76 (1999)

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Letter to the Editor

The BeppoSAX 1-8 keV cosmic background spectrum

A. Vecchi 1, S. Molendi 1, M. Guainazzi 2, F. Fiore 3 and A.N. Parmar 2

1 Istituto di Fisica Cosmica "G.Occhialini", Via Bassini 15, I-20133 Milano, Italy
2 Astrophysics Division, Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
3 BeppoSAX Science Data Center, Nuova Telespazio, via Corcolle 19, I-00131 Roma, Italy

Received 9 August 1999 / Accepted 28 August 1999


The spectrum of the 1.0-8.0 keV cosmic X-ray background (CXB) at galactic latitudes [FORMULA][FORMULA] has been measured using the BeppoSAX LECS and MECS instruments. The spectrum is consistent with a power-law of photon index [FORMULA] and normalization [FORMULA] photon cm-2 s- 1 keV-1 sr-1 at 1 keV. Our results are in good agreement with previous ROSAT PSPC (Georgantopuolos et al. 1996), ASCA GIS (Miyaji et al. 1998) and rocket (McCammon & Sanders 1990) measurements. On the contrary, previous measurements with the HEAO1 A2 (Marshall et al. 1980) and the ASCA SIS (Gendreau et al. 1995) instruments, are characterized by normalizations which are respectively 35% and 25% smaller than ours.

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

Send offprint requests to: S. Molendi (silvano@ifctr.mi.cnr.it)

© European Southern Observatory (ESO) 1999

Online publication: September 13, 1999