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Evidence for short term changes in the intensity and spectrum of hard X-rays from Cyg X-1

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The paper presents experimental evidence for the existence of fast intensity fluctuations with time scales of the order of a minute in the X-ray emission from Cyg X-1 at energies greater than 29 keV. Spectral variations over time intervals of 20–25 min are also observed in the same energy range. Whereas, similar intensity and spectral fluctuations have been reported earlier at lower energies the observations presented here is the first evidence for the existence of similar fluctuations at high energies.

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  1. Agrawal, P. C., Gokhale, G. S., Iyengar, V. S., Kunte, P. K., Manchanda, P. K., and Sreekantan, B. V.: 1972,Astrophys. Space Sci. 10, 271.

  2. Bolton, C. T.: 1972,Nature 235, 271.

  3. Frontera, F. and Fuligni, F.: 1975,Astrophys. J. 196, 597.

  4. Haymes, R. C. and Harnden, F. R. Jr.: 1970,Astrophys. J. 159, 1111.

  5. Heise, J., Mewe, R., Brinkman, A. C., den Boggende, A., Schrijver, J., Gronenschild, E., Parsignault, D., Grindlay, J., Schrier, E., Schnopper, H., and Gursky, H.: 1975,Nature 256, 106.

  6. Holt, S. S., Boldt, E. A., Serlemitsos, P. J., and Kaluzienski, L. J.: 1975, GSFC Report No. X-661-75-205.

  7. Parsignault, D. R., Epstein, A., Grindlay, J., Schreier, E., Schnopper, H., Gursky, H., Tanaka, Y., Brinkman, A. C., Heise, J., Schrijver, J., Mewe, R., Gronenschild, E., and den Boggende, A.: 1975,Proc. Symp. on Fast Transients in X- and Gamma Rays, COSPAR/IAU Varna, Bulgaria, May 30.

  8. Rothschild, R. E., Boldt, E. A., Holt, S. S., and Serlemitsos, P. J.: 1974,Astrophys. J. Lett. 170, L21.

  9. Sanford, P. W., Ives, J. C., Bell Burnell, S. J., Mason, K. O., and Murdin, P.: 1975,Nature 256, 109.

  10. Schrier, E., Gursky, H., Kellogg, E., Tananbaum, H., and Giacconi, R.: 1971,Astrophys. J. Lett. 170, L21.

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Jain, A.K., Jayanthi, U.B., Kasturirangan, K. et al. Evidence for short term changes in the intensity and spectrum of hard X-rays from Cyg X-1. Astrophys Space Sci 45, 433–438 (1976). https://doi.org/10.1007/BF00642677

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  • Lower Energy
  • Experimental Evidence
  • Energy Range
  • Similar Intensity
  • Short Term Change