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A expected bright radio flare of Cygnus X-3

ATEL # 1092; S.A.Trushkin, N.N. Bursov, N.A. Nizhelskij (SAO RAS)
on 1 Jun 2007; 8:33 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Sergei Trushkin (

Subjects: Radio, Millimeter, Gamma Ray, Request for Observations, Binaries, Black Holes, Transients

We detected a new powerful flare from the microquasar Cygnus X-3 with the RATAN-600 radio telescope on June 1. The measured flux densities are 3.2, 4.73, 3.42, 2.7, 2.34, 1.54 and 1.15 Jy at 1, 2.3, 4.8, 7.7, 11.2, 21.7 and 30 GHz respectively (MJD54252.05). Thus the spectral index is -0.54 at frequencies higher 2.3 GHz. The spectrum is similar to one on Jan 28 in the beginning of the powerful Jan-Feb flare of Cygnus X-3: . Last X-ray data (ATEL #1028, #1061 and #1081) from Swift-BAT and INTEGRAL clearly indicated a probable following jet ejection as it was observed in 2006 (ATEL #984). Indeed after a one year such jet activity Cygnus X-3 has left the high-soft state in February (see the RATAN/Swift-BAT light curves at and now entered this state again. The detected flare coincides with a fast increase of the hard X-ray flux during last two days (see

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