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Monitoring of Cyg X-3 giant flare with Medicina and the Sardinia Radio Telescope

ATel #9508; E. Egron, A. Pellizzoni (INAF-OAC), M. Giroletti, S. Righini, A. Orlati (INAF-IRA), M. N. Iacolina, A. Navarrini, M. Buttu, C. Migoni, A. Melis, R. Concu, G. P. Vargiu, M. Bachetti, M. Pilia, A. Trois, S. Loru, M. Marongiu (INAF-OAC)
on 19 Sep 2016; 23:27 UT
Credential Certification: Elise Egron (egron@oa-cagliari.inaf.it)

Subjects: Radio, Binary, Black Hole, Neutron Star

Following the detection of Cyg X-3 entering in an ultra soft X-ray state, a forthcoming giant flare was predicted by Trushkin et al. (ATel #9416). In fact, a significant radio flux increase was detected three weeks later, on 14-16 September 2016 (ATel #9502). We performed Cyg X-3 observations through single-dish imaging with the 64m Sardinia Radio Telescope (SRT) and On-The-Fly cross-scans with the 32m Medicina radio astronomical station on 19-20 September 2016. We detected a flux density of 12.4 +/- 0.4 Jy at 8.5 GHz (Medicina) and 12.6 +/- 0.3 Jy at 7.24 GHz (SRT), the latter measurement showing a possible trend in further flux increase during the 7h observation (about 0.15 Jy/hour). Cyg X-3 was also detected at 18.6 GHz with a flux density of 9.9 +/- 0.8 Jy (Medicina), providing a spectral index of -0.29 +/- 0.15.