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The predicted giant flare of Cyg X-3 occurs

ATel #9501; S. A. Trushkin, N. A. Nizhelskij, P. G. Tsybulev, G. V. Zhekanis (SAO RAS, Russia)
on 16 Sep 2016; 22:02 UT
Credential Certification: Sergei Trushkin (satr@sao.ru)

Subjects: Radio, Millimeter, Sub-Millimeter, Infra-Red, X-ray, Gamma Ray, >GeV, Binary, Black Hole

Referred to by ATel #: 9502, 10126

Three weeks ago we predicted (ATel #9416) that Cyg X-3 entered in the ''ultra-soft'' X-ray state and a giant flare are very probable. Later Cyg X-3 has indeed shown the relatively bright flare (ATel #9444), maximal fluxes were lower 700 mJy at 4-22 GHz and then the microquasar had again quenched. But during last three days (14-16 Sep 2016 = MJD57645.7-647.7) brightness of Cyg X-3 has increased from 140, to 1240 and then to 5920 mJy at 11.2 GHz. The dramatic changes of spectrum are given in the figure below. We see that the spectra were became optically thin at more lower frequencies as it follows from picture of ejections from compact core within accretion disk. Now spectrum is optically thick only at 2.3 GHz. Probably fluxes will increase farther, therefore any radio (at dm, cm, mm wavelengths) observations will be very interesting especially in the intra-day mode. Sure the multi-frequency VLBI mapping of the evolved jets (see VLBA maps of Cyg X-3 from Miller-Jones et al., 2004) will be very useful.

Radio spectra of Cyg X-3 during three last days