Interpretation of the optical flare in Cyg X-1 on May 14, 1997статья
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Аннотация:In May 1997, an optical flare was observed in the X-ray binary system Cyg X-1/V1357 Cyg, the strongest flare in the 26 years of its study. For 2.5 hours of observations on May 14/15, the system’s brightness exceeded the level of regular ellipsoidal variability by about 15% in U, 12% in B, and a mere 2% in V. The color properties of the flare correspond to the emission of a hydrogen plasma. The Balmer lines and the Balmer continuum fall within the U and B bands, but do not affect the V band. Estimates show that the observed characterstics correspond to a rapidly expanding cloud of gas (v~ 1500 km s\^-1) with a temperature of 20,000 K, which is observed when the optical depths in the Hβ_Hepsolon lines are of the order of unity. The size of the emitting region s ~ 3 x 10\^12 cm, the gas number density is ~ 3 x 10\^11 cm\^-3, and the expansion time is ~6 h.