Abstract
Simultaneous observations of hard X-ray and optical emission from Sco X-1 were carried out at Hyderabad, India, on April 16 and 19, 1972. During the first and the second observations Sco X-1 was on the average in a bright phase ofB=12.5 mag. and a slightly darker phase ofB=12.7 mag. respectively. During the first observation the X-ray intensity in the energy range 20–40 keV measured with balloon borne scintillation counters showed an enhancement of a factor of about two in coincidence with an optical flare ofB≅0.2 mag., whereas the apparent temperature derived from the X-ray spectrum observed in the energy range 20–35 keV showed no appreciable change. Both the X-ray intensity and the apparent temperature observed on April 19 are considerably lower than those observed on April 16. Taking into account the effect of radiative transfer in a hot plasma, the electron density and the optical depth for electron scattering of the plasma cloud are derived asn e ≈3×1016 cm−3 and τes ≈ 10 for the quiescent bright phase. The flare is explained by an increase of the plasma mass by about 30% and an increase of τes by τes ≈ 1 without appreciable change of the plasma temperature. The results on April 19 is interpreted as indicating that the quiescent dark phase may be characterized by a decrease of the plasma mass, its contraction and lower temperature.
Similar content being viewed by others
References
Canizares, C. R., Clark, G. W., Lewin, W. H. G., Schnopper, H. W., Sprott, G. F., Hjellming, R. M., and Wade, C. M.: 1973,Astrophys. J. Letters 179, L1.
Chodil, G., Mark, H., Rodrigues, R., Seward, F. D., Swift, C. D., Turiel, I., Hiltner, W. A., Wallerstein, G., and Mannery, E. J.: 1968,Astrophys. J. 154, 645.
Evans, W. D., Belian, R. D., Conner, J. P., Strong, I. B., Hiltner, W. A., and Kunkel, W. E.: 1970,Astrophys. J. Letters 162, L115.
Felten, J. E. and Rees, M. J.: 1972,Astron. Astrophys. 17, 226.
Hayakawa, S., Kasahara, I., and Matsuoka, M.: 1974, submitted toPubl. Astron. Soc. Japan.
Hudson, H. S., Peterson, L. E., and Schwartz, D. A.: 1970,Astrophys. J. Letters 159, L51.
Kitamura, T., Matsuoka, M., Miyamoto, S., Nakagawa, M., Oda, M., Ogawara, Y., Takagishi, K., Rao, U. R., Chitnis, E. V., Jananthi, U. B., Prakasa-Rao, A. S., and Bhandari, S. M.: 1971,Astrophys. Space Sci. 12, 378.
Lewin, W. H. G., McClintock, J. E., Ryckman, S. G., Glass, I. S., and Smith, W. B.: 1970,Astrophys. J. Letters 162, L109.
Mark, H., Price, R. E., Rodrigues, R., Seward, F. D., Swift, C. D., and Hiltner, W. A.: 1969,Astrophys. J. Letters 156, L67.
Matsuoka, M., Fujii, M., Miyamoto, S., Nishimura, J., Oda, M., Ogawara, Y., Ohta, S., Hayakawa, S., Kasahara, I., Makino, F., Tanaka, Y., Agrawal, P. C., Sreekantan, B. V., Hatanaka, Y., and Sreedhar Rao, S.: 1972a,Nature Phys. Sci. 236, 53.
Matsuoka, M., Fjii, M., Miyamoto, S., Nishimura, J., Hayakawa, S., Kasahara, I., Makino, F., Tanaka, Y., Agrawal, P. C. and Sreekantan, B. V.: 1972b,Astrophys. Space Sci. 18, 472.
Matsuoka, M., Miyamoto, S., Nishimura, J., Oda, M., Ogawara, Y., Ohtsuka, Y., Hayakawa, S., Kasahara, I., Makino, F., Tanaka, Y., Agrawal, P. C., Sreekantan, B. V., Manabe, M., Mikami, Y., Lokanandham, B., Raghavender Rao, C., Sreedhar Rao, S., and Swaminathan, R.: 1973, submitted toNature Phys. Sci.
Nishimura, J.: 1973, submitted toNature Phys. Sci.
Neugebauer, G., Oke, J. B., Becklin, E., and Garmire, G.: 1969,Astrophys. J. 155, 1.
Overbeck, J. W. and Tananbaum, H. D.: 1968,Astrophys. J. 153, 899.
Pelling, R. M.: 1971, Tesis, University of California, San Diego.
Peterson, L. E. and Jacobson, A. S.: 1966,Astrophys. J. 145, 962.
Riegler, R., Boldt, E., and Serlemitsos, P.: 1970,Nature 226, 1041.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Kasahara, I. Simultaneous hard X-ray and optical observations of Sco X-1 and a model of semi-opaque X-ray sources. Astrophys Space Sci 29, 191–210 (1974). https://doi.org/10.1007/BF00642723
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00642723