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AGILE Detection of Gamma-Ray Emission from the Microquasar Cygnus X-3

ATel #9429; G. Piano (INAF/IAPS), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Bulgarelli (INAF/IASF-Bo), F. Verrecchia (ASDC and INAF/OAR), I. Donnarumma, P. Munar-Adrover (INAF/IAPS), G. Minervini (CIFS and INAF/IAPS), V. Fioretti, A. Zoli (INAF/IASF-Bo), C. Pittori, F. Lucarelli (ASDC and INAF/OAR), S. Vercellone (INAF/IASF-Pa), E. Striani (CIFS and INAF/IAPS), M. Cardillo (INAF/OA-Arcetri and INAF/IAPS), 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, S. Sabatini, V. Vittorini (INAF/IAPS), G. Pucella, M. Rapisarda (ENEA-Frascati), G. Di Cocco, F. Fuschino, M. Galli, C. Labanti, M. Marisaldi (INAF/IASF-Bo), 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), S. Colafrancesco (INAF/OAR and Wits University), N. Parmiggiani (University of Modena and Reggio Emilia), A. Ferrari (Univ. Torino and CIFS), A. Antonelli (ASDC and INAF/OAR), P. Giommi (ASDC), L. Salotti, G. Valentini, and F. D'Amico (ASI)
on 30 Aug 2016; 15:52 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Giovanni Piano (giovanni.piano@iaps.inaf.it)

Subjects: Radio, X-ray, Gamma Ray, >GeV, Request for Observations, Binary, Black Hole, Transient

The AGILE-GRID detector is revealing gamma-ray emission above 100 MeV from a source positionally consistent with the microquasar Cygnus X-3. Integrating from 2016-08-28 UT 09:00:00 to 2016-08-30 UT 09:00:00 (MJD: 57628.375 - 57630.375), a preliminary multi-source likelihood analysis detects a gamma-ray flux F(>100 MeV) = (4.0 +/- 1.4) x 10^-6 photons/cm^2/s with a significance near 4 sigma.

Cygnus X-3 is currently in a very low state in hard X-rays (Swift/BAT, 15-50 keV; http://swift.gsfc.nasa.gov/results/transients/CygX-3/ ), and is also observed to be in a low radio state (RATAN-600, ATel #9416). As previously detected, low states of radio and hard X-ray emissions from Cyg X-3 may precede outbursts and plasmoid ejections with gamma-ray flaring above 100 MeV (Tavani et al., Nature, 462, 620, (2009); Fermi LAT Collaboration et al., Science, 326, 1512 (2009); Piano et al., A&A, 545, A110 (2012)). Therefore, Cyg X-3 might flare possibly with plasmoid ejections in the next few days.

We strongly encourage multi-frequency observations of Cygnus X-3.