Abstract
The hydrogen column density along the line of sight to Cyg X-1 is 7×1021 cm−2 as determined from the extinction of its optical counterpart HD 226 868. This value may be used to interpret soft X-ray measurements, including those previously reported, where it is not possible to determine the column density independently from the intrinsic spectral function. The correction for interstellar absorption is larger than previously thought. Application to an old observation suggests that an intense soft X-ray component was present in Cyg X-1, even though the data at ∼1 keV suggests that it was probably in a low state. This is consistent with the picture of Cyg X-1 suggested by Price and Thorne, in which transitions in Cyg X-1 are attributed to changes in the high energy cut-off of an intense soft component.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Becklin, E. E., Kristian, J., Neugebauer, G., and Wynn-Williams, C. G.: 1972,Nature Phys. Sci. 239, 130.
Bregman, J., Butler, D., Kemper, E., Koski, A., Kraft, R. P., and Stone, R. P. S.: 1973,Astrophys. J. Letters 185, L117.
Bunner, A. N., Coleman, P. H., Kraushaar, P. H., and McCammon, D.: 1972,Astrophys. Letters 12, 165.
Gerend, D. J.: 1974 (private communication).
Giacconi, R., Gorenstein, P., Gursky, H., Usher, P. D., Waters, J. R., Sandage, A., Osmer, P., and Peach, J. V.: 1967,Astrophys. J. 148, 429.
Gorenstein, P.: 1975,Astrophys. J. 198, 95.
Gursky, H., Gorenstein, P., Kerr, F., and Grayzeck, E.: 1971,Astrophys. J. Letters 167, L115.
Jones, C., Forman, W., Tananbaum, H., Schreier, E., Gursky, H., Kellogg, E., and Giacconi, R.: 1973,Astrophys. J. Letters 181, L43.
Jones, C., Giacconi, R., Forman, W., and Tananbaum, H.: 1974,Astrophys. J. Letters 191, L71.
Krzeminski, W.: 1974,Astrophys. J. Letters 192, L135.
Kwok Li, F. and Clark, G. W.: 1974,Astrophys. J. Letters 191, L27.
Liller, W.: 1974 (private communication).
Margon, B., Bowyer, S., and Stone, R. P. S.: 1973,Astrophys. J. Letters 185, L113.
Murray, S.: 1974 (private communication).
Ryter, C., Cesarsky, J. and Audouze, J.: 1975,Astrophys. J. 198, 103.
Sandage, A. R., Osmer, P., Giacconi, R., Gorenstein, P., Gursky, H., Waters, J., Bradt, H., Garmire, G., Sreekantan, B. V., Oda, M., Osawa, K., and Jugaku, J.: 1966,Astrophys. J. 146, 316.
Seward, F. D., Burginyon, G. H., Grader, R. J., Hill, R. W., and Palmieri, T. M.: 1972,Astrophys. J. 178, 131.
Tananbaum, H., Gursky, H., Kellogg, E., Giacconi, R., and Jones, C.: 1972,Astrophys. J. Letters 177, L5.
Thorne, K. S. and Price, R. H.: 1975,Astrophys. J. Letters 195, L101.
Vidal, N. V., Wickramasinghe, D. T., Peterson, B. H., and Bessell, M. S.: 1974,Astrophys. J. Letters 191, L23.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Gorenstein, P. Interstellar absorption and variable soft X-ray component in Cygnus X-1. Astrophys Space Sci 42, 189–192 (1976). https://doi.org/10.1007/BF00645541
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00645541