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A new state of quenched radio emission from microquasar Cyg X-3

ATel #9416; S. A. Trushkin, N. A. Nizhelskij, P. G.Tsybulev, G. V. Zhekanis (SAO RAS, Russia)
on 26 Aug 2016; 13:42 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Sergei Trushkin (satr@sao.ru)

Subjects: Radio, Millimeter, Infra-Red, X-ray, Gamma Ray, VHE, Binary, Black Hole, Transient

Referred to by ATel #: 9429, 9444, 9481, 9501, 9508, 10126

During last three days (MJD 57622-625) the radio fluxes decreased from quiescent level 100-200 mJy to 10-50 mJy at 4.6, 8.2 and 11.2 GHz (on 23-25 Aug 2016), as the RATAN-600 radio telescope monitoring measurements showed. The dramatic quenching of the hard X-ray fluxes were detected with the Swift/BAT Hard X-ray Transient Monitor at 15-50 keV (see http://swift.gsfc.nasa.gov/results/transients/CygX-3/ and Krimm et al., 2013) also. The 1-day X-ray fluxes decreased from 150-200 mCrab to 7-10 mCrab. Such radio behaviour was detected by Waltman et al. (1996) and it could be a forerunner of the following (after 1-3 weeks) powerful radio flare (more than ~3 Jy). Koljonen et al. (2010) showed that Cyg X-3 follows especial track on the hardness-intensity diagram, running through a so-called "ultra-soft X-ray state" before the powerful ejections (radio jets). Thus we have strong reason to expect a giant flare during next 10-30 days.

We plotted the RATAN radio data and Swift hard X-ray data during last 75 days. It is worth to notice we have detected the high anti-correlation between quiescent radio and X-ray emission during last almost 2000 days. Recently we have detected some small optically thick flares during the null values of the X-ray flux on 5, 15 and July 2016. The last such event was detected on 20-21 Aug 2016 (MJD 57621-622), just before the current "nulling". Now the former anti-correlation changed a sign: now the small radio fluxes correlated with very small hard X-ray fluxes. We continue the RATAN daily observations and any intra-day radio observations will be very useful.

The light curves (RATAN) and at 15-50 keV (Swift) of Cyg X-3