Abstract
HER X-1 was observed with the Copernicus satellite X-ray detectors on June 5 this year. This date was chosen because it was predicted to be within an “extended low” of the 35-day cycle reported by Giacconi et al.1. The purpose of the observation was to search for the steady soft component, hypothesized2,3 to account for the persistence through the “extended lows” of the ∼1.5 mag amplitude, 1.7 d period, optical variations which are generally attributed to heating of one face of the companion star by the X-ray source. We report here the unexpected result that Her X-1 was detected in the 4 to 12 keV channel (overlapping with the energy range covered by Uhuru), at an intensity comparable with the previously measured “high state” intensity.
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References
Giacconi, R., Gursky, H., Kellogg, E., Levinson, R., Schreier, E., and Tananbaum, H., Astrophys. J. (in the press).
Avni, Y., Bahcall, J. N., Joss, P. C., Bahcall, N. A., Lamb, F. K., Pettick, C. J., and Pines, D., Astrophys. J. (in the press).
Pringle, J. E., Nature phys. Sci., 243, 90 (1973).
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FABIAN, A., PRINGLE, J. & REES, M. Long-term Behaviour of Hercules X-1. Nature 244, 212–213 (1973). https://doi.org/10.1038/244212a0
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DOI: https://doi.org/10.1038/244212a0
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