Abstract
Cygnus X-1 was observed from 3 November until 9 November, 1974, using the hard X-ray (1–28 keV) and soft X-ray (1–8 keV) experiment on board the Astronomical Netherlands Satellite. On three occasions, on 4 and 5 November, the X-ray spectrum was observed to be harder, while the flux intensity in the 1–7 keV ranges decreased by ∼50% from its quiescent value. These events occurred near and following the time of superior conjunction of the likely optical counterpart HDE 226 868. These events appear to be the same as previously reported absorption dips and reveal this phenomenon to be more complex than had been believed. A systematic study of the X-ray spectral variations in these energy bands, on a time scale of 64 seconds over the period of the spectroscopic binary, is presented.
Similar content being viewed by others
References
Brinkman, A. C., Heise, J., and Jager, C. de: 1974,Philips Tech. Rev. 34, 43.
Brown, R. H. and Gould, R. J.: 1970,Phys. Rev. D1, 2252.
Giacconi, R.: 1975, 7th Texas Symposium on Relativistic Astrophysics,Annals of the New York Academy of Sciences,262, 312.
Gorenstein, P.: 1976,Astrophys. Space Sci. 42, 189.
Gursky, H., Schnopper, H., and Parsignault, D.: 1975,Astrophys. J. Letters 201, L127.
Li, F. K. and Clark, G.: 1974,Astrophys. J. Letters 191, L27.
Margon, B., Lampton, M., Bowyer, S., and Cruddace, R.: 1975,Astrophys. J. 197, 25.
Mason, K. O., Hawkins, F. J., Sanford, P., Murdin, P., and Savage, A.: 1974,Astrophys. J. Letters 192, L65.
Sanford, P. W., Mason, K. O., Hawkins, F. J., Murdin, P., and Savage, A.: 1974,Astrophys. J. Letters 190, L55.
Tananbaum, H., Gursky, H., Kellogg, E. M., and Giacconi, R.: 1972,Astrophys. J. Letters 177, L5.
Author information
Authors and Affiliations
Additional information
On leave from Institute of Space and Aeronautical Science, University of Tokyo.
Rights and permissions
About this article
Cite this article
Parsignault, D.R., Epstein, A., Grindlay, J. et al. ANS observations of Cygnus X-1. Astrophys Space Sci 42, 175–184 (1976). https://doi.org/10.1007/BF00645539
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00645539