New giant radio flare of microquasar Cyg X-3
ATel #17742; S. A. Trushkin, P. G. Tsybulev, N. N. Bursov, A. V. Shevchenko (SAO RAS, Russia)
on 6 Apr 2026; 10:08 UT
Credential Certification: Sergei Trushkin (satr@sao.ru)
Subjects: Radio, Gamma Ray, Request for Observations, Binary, Black Hole
Referred to by ATel #: 17746
We carry out the multi-frequency monitoring of the Galactic microquasars with the RATAN-600 radio telescope and on 6 April 2026 detected the giant flare from the microquasar Cygnus X-3 at frequencies 4.7-30 GHz. It was the first increase of radio emission from 22 February, when we detected small flare with fluxes from 0.5 to 1.2 Jy at frequencies 1.24-11.2 GHz. Later Cyg X-3 was in so-called hyper-soft X-ray state during at least 30 days, as we can propose from very low hard X-ray emission (10-20 keV, MAXI), while soft X-ray (2-4 keV, MAXI) fluxes became at high levels. During last weeks the microquasar had shown very low radio fluxes less 30 mJy 4.7 GHz (RATAN-600), often drop down to a detection level 3-5 mJy.
Today (MJD 61132.200) the flux increased up to 6.6 Jy at 11.2 GHz. The spectral index was
about -0.40 (S_nu ~ nu^alpha) at frequencies higher 11 GHz, meanwhile fluxes 2.99 Jy at 4.7 GHz and
5.70 Jy at 8.2 GHz determine the spectral index +1.16. Thus probably the radio fluxes will increase during next some days. Any future TOO observations at X-rays and Gamma-rays, and mm-wavelengths could be useful.
Radio spectrum of Cyg X-3 on 6 April 2026
