Letter | Published:

Cygnus X-1—a Spectroscopic Binary with a Heavy Companion ?


WE have reported1 that the spectrum, colours and interstellar features in the star HD 226868, which is coincident with the X-ray star Cygnus X-1 and a radio star2,3, were those of a normal BOIb supergiant. We made measurements of the radial velocity of the star from August 1971 to October 1971 and find it to be a velocity variable, whose changes of velocity correlate with changes in the X-ray flux.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. 1

    Murdin, P., and Webster, B. L., Nature, 233, 110 (1971).

  2. 2

    Braes, L. L. E., and Miley, G. K., Nature, 232, 246 (1971).

  3. 3

    Rappaport, S., Zaumen, W., and Doxsey, R., Astrophys. J. Lett., 168, L17 (1971).

  4. 4

    Stothers, R., and Lloyd Evans, T., Observatory, 90, 186 (1970).

  5. 5

    Slettebak, A., and Howard, R. E., Astrophys. J., 120, 102 (1955).

  6. 6

    Allen, C. W., Astrophysical Quantities (second ed.) (University of London Press, 1964).

  7. 7

    Dolan, J. F., Space Sci. Rev., 10, 830 (1971).

  8. 8

    Dolan, J. F., Nature, 233, 109 (1971).

  9. 9

    Agrawal, P. C., Gokhale, G. S., Iyengar, V. S., Kunte, P. K., Manchanda, R. K., and Sreekantan, B. V., Nature, 232, 38 (1971).

  10. 10

    Plavec, M., Bull. Astron. Inst. Czech., 18, 253 (1967).

  11. 11

    Oda, M., Gorenstein, P., Gursky, H., Kellogg, E., Schreier, E., Tannanbaum, H., and Giacconi, R., Astrophys. J. Lett., 166, L1 (1971).

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.