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AGILE detection of transient gamma-ray activity from Cygnus X-3 during a prolonged quenched state

ATel #14780; G. Piano (INAF/IAPS), A. Bulgarelli (INAF/OAS-Bo), F. Verrecchia, C. Pittori (SSDC and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), V. Fioretti, N. Parmiggiani, A. Addis, L. Baroncelli, A. Di Piano (INAF/OAS-Bo), F. Lucarelli (SSDC and INAF/OAR), S. Vercellone (INAF/OA-Brera), M. Cardillo, A. Ursi, C. Casentini (INAF/IAPS), I. Donnarumma (ASI), F. Gianotti, M. Trifoglio (INAF/OAS-Bo), A. Giuliani, S. Mereghetti, P. Caraveo, F. Perotti (INAF/IASF-Mi), A. Chen (Wits University), A. Argan, E. Costa, E. Del Monte, Y. Evangelista, M. Feroci, L. Foffano, I. Lapshov, E. Menegoni, L. Pacciani, P. Soffitta, V. Vittorini (INAF/IAPS), F. Lazzarotto (INAF/OAPD), G. Di Cocco, F. Fuschino, M. Galli, C. Labanti (INAF/OAS-Bo), M. Marisaldi (University of Bergen), A. Pellizzoni, M. Pilia, A. Trois (INAF/OA-Cagliari), G. Barbiellini (INFN Trieste), F. Longo (Univ. Trieste and INFN Trieste), E. Vallazza (INFN Milano Bicocca), A. Morselli, P. Picozza (INFN and Univ. Roma Tor Vergata), M. Prest (Univ. dell'Insubria), P. Lipari, D. Zanello (INFN and Univ. Roma Sapienza), P. W. Cattaneo, A. Rappoldi (INFN Pavia), A. Ferrari (Univ. Torino and CIFS), F. Paoletti (East Windsor RSD Hightstown and INAF/IAPS), L. A. Antonelli (INAF/OAR), P. Giommi, L. Salotti, G. Valentini, and F. D'Amico (ASI)
on 13 Jul 2021; 14:12 UT
Credential Certification: Giovanni Piano (giovanni.piano@inaf.it)

Subjects: Gamma Ray, >GeV, Binary, Black Hole, Transient

Referred to by ATel #: 15009

The microquasar Cyg X-3 is currently in a deep and prolonged quenched state. The hard X-ray emission is currently not detected (Swift/BAT, 15-50 keV; http://swift.gsfc.nasa.gov/results/transients/CygX-3/ ).

AGILE found evidence of transient gamma-ray emission above 100 MeV from Cygnus X-3. Integrating from 2021-07-11 UT 00:00:00 to 2021-07-13 UT 00:00:00 (MJD: 59406.0 - 59408.0), a preliminary multi-source likelihood analysis yields a detection with a significance of 4 sigma and a gamma-ray flux F(>100 MeV) = (3 +/- 1) x 10^-6 photons/cm^2/s.

Before this recent activity, AGILE detected transient gamma-ray emission from the microquasar at the beginning of the quenched state (2021 May, 24-26, MJD: 59358.875 - 59360.250, ATel #14662). As observed several times in the past, Cyg X-3 might produce gamma-ray activity, possibly preceding major radio flares with plasmoid ejections, when it is emerging from such a quenched state (Tavani et al., Nature, 462, 620, 2009). Multifrequency observations of Cyg X-3 during this interesting phase are strongly encouraged.

The AGILE-GRID detection was obtained while AGILE is observing in spinning mode, surveying a large fraction of the sky each day. The source can be monitored with the public mobile application "AGILEScience" developed by the AGILE Team, available for both Android and iOS devices.