AGILE gamma-ray observations of Cygnus X-3 during the current quenched/hypersoft state
ATel #13423; G. Piano (INAF/IAPS), F. Verrecchia (SSDC and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), C. Pittori, F. Lucarelli (SSDC and INAF/OAR), S. Vercellone (INAF/OA-Brera), M. Cardillo, A. Ursi, C. Casentini (INAF/IAPS), A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/IASF-Bo), I. Donnarumma (ASI), F. Gianotti, M. Trifoglio (INAF/IASF-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, F. Lazzarotto, I. Lapshov, L. Pacciani, P. Soffitta, V. Vittorini (INAF/IAPS), G. Di Cocco, F. Fuschino, M. Galli, C. Labanti (INAF/IASF-Bo), M. Marisaldi (University of Bergen), A. Pellizzoni, M. Pilia, A. Trois (INAF/OA-Cagliari), G. Barbiellini, E. Vallazza (INFN Trieste), F. Longo (Univ. Trieste and INFN Trieste), 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, P. Giommi, L. Salotti, G. Valentini, and F. D'Amico (ASI)
on 28 Jan 2020; 15:30 UT
Credential Certification: Giovanni Piano (giovanni.piano@inaf.it)
Subjects: Gamma Ray, >GeV, Binary, Black Hole, Transient
The microquasar Cyg X-3 entered a quenched/hypersoft state at the beginning of January 2020 (Swift/BAT, 15-50 keV; http://swift.gsfc.nasa.gov/results/transients/CygX-3/ ). Cyg X-3 showed a hard-to-soft X-ray spectral transition.
AGILE found evidence of transient gamma-ray emission above 100 MeV from Cygnus X-3 during this spectral change. Integrating from 2020-01-08 UT 00:00:00 to 2020-01-10 UT 00:00:00 (MJD: 58856.0 - 58858.0), a preliminary multi-source likelihood analysis yields a 2-day detection with a significance of 3.3 sigma and a gamma-ray flux F(>100 MeV) = (3 +/- 1) x 10^-6 photons/cm^2/s. For a longer integration (8 days), from 2020-01-02 UT 00:00:00 to 2020-01-10 UT 00:00:00 (MJD: 58850.0 - 58858.0), a preliminary multi-source likelihood analysis yields a detection with a significance of 4.2 sigma and a gamma-ray flux F(>100 MeV) = (1.9 +/- 0.6) x 10^-6 photons/cm^2/s.
As detected several times in the past, when Cyg X-3 emerges from such a quenched state, it might show gamma-ray activity, possibly preceding major radio flares with plasmoid ejections. 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.
