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Single-dish and VLBI observations of Cygnus X-3 during the 2016 giant flare episode

Egron, Elise and Pellizzoni, A. and Giroletti, M. and Righini, S. and Stagni, M. and Orlati, A. and Migoni, C. and Melis, A. and Concu, R. and Barbas, L. and Buttaccio, S. and Cassaro, P. and De Vicente, P. and Gawronski, M. P. and Lindqvist, M. and Maccaferri, G. and Stanghellini, C. and Wolak, P. and Yang, J. and Navarrini, A. and Loru, S. and Pilia, M. and Bachetti, M. and Iacolina, M. N. and Buttu, M. and Corbel, S. and Rodriguez, J. and Markoff, S. and Wilms, J. and Pottschmidt, K. and Bel, M. Cadolle and Kalemci, Emrah and Belloni, T. and Grinberg, V. and Marongiu, M. and Vargiu, G. P. and Trois, A. (2017) Single-dish and VLBI observations of Cygnus X-3 during the 2016 giant flare episode. Monthly Notices of the Royal Astronomical Society, 471 (3). pp. 2703-2714. ISSN 0035-8711 (Print) 1365-2966 (Online)

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Official URL: http://dx.doi.org/10.1093/mnras/stx1730

Abstract

In September 2016, the microquasar Cygnus X-3 underwent a giant radio flare, which was monitored for 6 days with the Medicina Radio Astronomical Station and the Sardinia Radio Telescope. Long observations were performed in order to follow the evolution of the flare on a hourly scale, covering six frequency ranges from 1.5 GHz to 25.6 GHz. The radio emission reached a maximum of 13.2 +/- 0.7 Jy at 7.2 GHz and 10 +/- 1 Jy at 18.6 GHz. Rapid flux variations were observed at high radio frequencies at the peak of the flare, together with rapid evolution of the spectral index: alpha steepened from 0.3 to 0.6 within 5 hours. This is the first time that such fast variations are observed, giving support to the evolution from optically thick to optically thin plasmons in expansion moving outward from the core. Based on the Italian network (Noto, Medicina and SRT) and extended to the European antennas (Torun, Yebes, Onsala), VLBI observations were triggered at 22 GHz on five different occasions, four times prior to the giant flare, and once during its decay phase. Flux variations of 2-hour duration were recorded during the first session. They correspond to a mini-flare that occurred close to the core ten days before the onset of the giant flare. From the latest VLBI observation we infer that four days after the flare peak the jet emission was extended over 30 mas.

Item Type:Article
Uncontrolled Keywords:stars: flare; stars: individual: Cyg X-3; radio continuum: stars; X-rays: binaries
Subjects:Q Science > QB Astronomy > QB460-466 Astrophysics
ID Code:35679
Deposited By:Emrah Kalemci
Deposited On:11 Aug 2018 15:19
Last Modified:11 Aug 2018 15:19

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