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Cyg X-3 is in the active state

ATel #952; T. Tosaki (NRO NAOJ), K. Nakanishi (NRO NAOJ) M. Tsuboi (NRO NAOJ), S. Trushkin (SAO RAS), O. Kameya (NAOJ Mizushima) K. Fujisawa (Yamaguchi-U), T. Kotani (Tokyo Tech), N. Kawai (Tokyo Tech)
on 24 Nov 2006; 16:22 UT
Credential Certification: T. Kotani (kotani@hp.phys.titech.ac.jp)

Subjects: Radio, Millimeter, Black Hole, Transient

Referred to by ATel #: 984, 1028

We report that the microquasar Cyg X-3 (RA=20:32:25.78, Dec=40:57:27.9 J2000) has entered the flaring state and would request for followup observations at all frequencies. In the monitoring program of microquasars with the RATAN-600 radio telescope (Trushkin et al., astro-ph/0611550), the flux density at 4.8 GHz of Cyg X-3 was found to drop from 191+-5 mJy at Nov 7.57 (UT) to 21+-3 mJy on Nov 8.57 (UT), that is a quenched state followed by a flaring event with fluxes reaching 1-10 Jy (Waltman et al., 1994, AJ, 108, 179; ATel #727, #828). On Nov 16, about eight days after it entered the quenched state, the rise of a peak has been detected with the Nobeyama Millimeter Array (NMA) and RATAN-600. The flux densities on Nov 16.3 at 97.782 GHz and 109.782 GHz were 160 mJy and 140 mJy, respectively. The flux density at 4.8 GHz was 280 mJy on Nov 16.55 (UT), and reached a maximum value of 2655 mJy on Nov 19.54 (UT). From Nov 21.3 (UT) to Nov 22.3 (UT) the millimeter flux densities have risen from 165 to 3000 mJy then showed a rapid decay with a time scale of a few tens min. The RATAN spectrum on Nov 22.53 (UT) is well fitted by a power-law with spectral index -0.19 from 1 to 30 GHz. The total spectrum from 1 GHz to 100 GHz on Nov 22 can not be expressed with an optically thin power-low model but shows a high-frequency component with a peak above 100 GHz and/or with a short lifetime, less than 6-8 hours. After the first rise at Nov 16, the flux densities show two peaks with an interval of 3 days. This spectral and temporal behavior suggests that a high-energy jet-ejection event is in progress in this system. Plots of the peak spectra are available at: http://www.hp.phys.titech.ac.jp/kotani/cygx3/26.html and the current RATAN-600 simultaneous spectra (1-30 GHz) are available at: http://cats.sao.ru/~satr/XB/CygX-3/c3_sp_2006nov.png