Abstract
Cygnus X-l, a black hole candidate of long standing, emits X-rays whose flux varies on many timescales1,2. The X-rays are commonly thought to be due to inverse Compton scattering of low-energy photons by a cloud of hot plasma, with temperature ∼108-109 K, near the black hole3,4. According to this model, variations in the flux of high-energy X-rays should occur somewhat later than similar variations in lower-energy X-rays. Using the large-area proportional counters (LAC) on the Ginga satellite, we have observed Cygnus X-l in its low state, and complex cross-spectrum analysis of the data reveals that the delay of the high-energy X-rays with respect to the low increases from approximately 2 ms to several seconds for periods from 0.1 to 300 s. This is inconsistent with the inverse Compton scattering model of Cygnus X-l.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 51 print issues and online access
$199.00 per year
only $3.90 per issue
Buy this article
- Purchase on Springer Link
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
References
Oda, M. Sp. Sci. Rev. 20, 757–813 (1977).
Liang, E. P. & Nolan, P. L. Sp. Sci. Rev. 38, 353–384 (1984).
Shapiro, S. L., Lightman, A. P. & Eardley, D. M. Astrophys. J. 204, 187–199 (1976).
Sunyaev, R. A. & Trumper, J. Nature 279, 506–508 (1979).
Brinkman, A. C. et al. Astrophys. J. 188, 603–608 (1974).
Weisskopf, M. C., Kahn, S. M. & Sutherland, P. G. Astrophys. J. 199, L147–L151 (1975).
Priedhorsky, W. et al. Astrophys. J. 233, 350–363 (1979).
Nolan, P. L. Astrophys. J. 246, 494–501 (1981).
Page, C. G., Bennetts, A. J. & Ricketts, M. J. Sp. Sci. Rev. 30, 369–371 (1981).
Page, C. G. Sp. Sci. Rev. 40, 387–390 (1985).
Van der Klis., et al. Astrophys. J. 319, L13–L18 (1987).
Stella, L. et al. Astrophys. J. 327, L13–L16 (1988).
Makino, M. & the Astro-C team. Astrophys. Lett. Commun. 25, 223–233 (1987).
Bendat, J. S. & Piersol, A. G. Random Data: Analysis and Measurement Procedures 193 (Wiley, New York, 1971).
Sunyaev, R. A. & Titarchuk, L. G. Astr. Astrophys. 86, 121–138 (1980).
Payne, D. G. Astrophys. J. 237, 951–963 (1980).
Stollman, G. M., Hasinger, G. Lewin, W. H. G., van der Klis, M., & van Paradijs, J. Mon. Not. R. astr. Soc. 227, 7–12 (1987).
Mitsuda, K. & the Ginga team in The Physics of Compact Objects: Theory Versus Observations (eds Filipov, L. & White, N. E.) (Pergamon, Oxford, in the press).
White, N. E., Stella, L. & Parmar, A. N. Astrophys. J. 324, 363–378 (1988).
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Miyamoto, S., Kitamoto, S., Mitsuda, K. et al. Delayed hard X-rays from Cygnus X-l. Nature 336, 450–452 (1988). https://doi.org/10.1038/336450a0
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1038/336450a0
Comments
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.
