2–20 keV X-ray sky background
1970 ◽
Vol 37
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pp. 309-314
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The diffuse background of 2–20 keV X-rays over a band of the sky extending from Scorpius to the North galactic pole is found to be isotropic to within 5%, with a spectrum given bywheren= (1.35 ±0.100.07).A comparison with spectra at higher energies indicates that the lower energy spectrum is flatter, corresponding to an apparent unit change in spectral index within the band 20–80 keV. A spectral break in this energy region has been discussed in connection with the collisional energy loss lifetime for metagalactic protons that radiate X-rays via inverse bremsstrahlung collisions with the ambient electrons of the intergalactic medium (Boldt and Serlemitsos, 1969; Hayakawa, 1970).