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Enhanced gamma-ray emission detected by AGILE from the Cygnus X-3 region

ATel #3386; G. Piano, M. Tavani (INAF/IASF Roma), A. Bulgarelli (INAF/IASF Bologna), E. Striani, M. Cardillo (Univ. Tor Vergata), S. Sabatini (INAF/IASF Roma), F. Gianotti, M. Trifoglio (INAF/IASF Bologna), C. Pittori, F. Verrecchia, F. Lucarelli (ASDC), A. Argan, A. Trois, G. De Paris, E. Costa, I. Donnarumma, M. Feroci, L. Pacciani, E. Del Monte, F. Lazzarotto, P. Soffitta, Y. Evangelista, I. Lapshov, V. Vittorini, M. Giusti (INAF/IASF Roma), P. Caraveo, A. Chen, A. Giuliani, S. Mereghetti, F. Perotti (INAF/IASF Milano), M. Marisaldi, G. Di Cocco, C. Labanti, F. Fuschino, M. Galli (INAF/IASF Bologna), G. Pucella, M. Rapisarda (ENEA-Roma), S. Vercellone, F. D'Ammando (IASF-Pa), A. Pellizzoni, M. Pilia (INAF/OA-Cagliari), G. Barbiellini, F. Longo (INFN Trieste), P. Picozza, A. Morselli (INFN and Univ. Tor Vergata), M. Prest (Universita` dell'Insubria), P. Lipari, D. Zanello (INFN Roma-1), P. W. Cattaneo, A. Rappoldi (INFN Pavia), P. Giommi, P. Santolamazza (ASDC), G. Valentini, L. Salotti (ASI).
on 29 May 2011; 17:13 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Marco Tavani (tavani@iasf-roma.inaf.it)

Subjects: X-ray, Gamma Ray, Transient

Referred to by ATel #: 3389, 8591

AGILE is detecting enhanced gamma-ray emission from a source positionally consistent with the microquasar Cygnus X-3.

Integrating during the period 2011-05-28 07:58:37 UT to 2011-05-29 06:02:51 UT (MJD=55709.33-55710.25) the AGILE-GRID detected gamma-ray emission above 100 MeV from a source at Galactic coordinates (l, b) = (79.8, 0.3) +/- 0.8 (stat.) +/- 0.1 (syst.) deg, and flux F > 300 x 10^-8 photons/cm^2/s above 100 MeV (1-day multi-source-analysis significance in spinning mode ~4 sigma). The multi-source likelihood analysis was carried out taking into account the gamma-ray sources in the field including the nearby pulsars (PSR J2021+3651, PSR J2021+4026, PSR J2032+4127).

We notice that the hard X-ray lightcurve of Cygnus X-3 as monitored by the BAT/Swift instrument (public data available at http:///heasarc.gsfc.nasa.gov/docs/swift/results/transients/CygX-3 ) shows an overall decreasing trend starting on MJD ~ 55680. This trend of decreasing hard X-ray emission in conjunction with gamma-ray flaring activity of Cygnus X-3 was already detected several times (Tavani et al., 2009).

We strongly encourage multifrequency observations of Cygnus X-3.