Abstract
AN objection1 has recently been raised to the use of X-ray production by suprathermal proton bremsstrahlung (SPB) to explain the X-ray observations at 1/4 keV2: it was pointed out that the soft X-ray flux measured at low galactic latitudescould not be reproduced on the basis of SPB production in the plane when account is taken both of absorption of the X-rays by photoionization in the galaxy and of the cut-off in the proton spectrum due to ionizing collisions in the interstellar gas. The purpose of the original paper2 was, however, a calculation of the diffuse X-ray background at 1/4 keV which could be expected to be incident on the galaxy from SPB interactions occurring in the intergalactic medium. As such, it made no reference to X-ray production in the galactic plane; further, since the computed X-ray spectra were those incident on the periphery of the galaxy, it is clear that any objection to these results based on a neglect of absorption in the galaxy is not applicable.
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References
De Freitas Pacheco, J. A., Nature, 227, 1230 (1970).
Brown, R. L., Astrophys. J., 159, L187 (1970).
Bunner, A. N., Coleman, P. C., Kraushaar, W. L., McCammon, D., Palmieri, T. M., Shilepsky, A., and Ulmer, U., Nature, 223, 1222 (1969).
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BROWN, R. The 1/4 keV X-ray Background: a Reply. Nature Physical Science 229, 85 (1971). https://doi.org/10.1038/physci229085a0
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DOI: https://doi.org/10.1038/physci229085a0