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AGILE detection of gamma-ray emission from the Cygnus X-3 region

ATEL # 2609; A. Bulgarelli (INAF/IASF Bologna), E. Striani (Univ. Tor Vergata), S. Sabatini, G. Piano, M. Tavani (INAF/IASF Roma), F. Gianotti, M. Trifoglio (INAF/IASF Bologna), G. Pooley (Cavendish Lab., Cambridge UK), M. McCollough (Smithsonian Astrophys. Observatory),C. Pittori, F. Verrecchia (ASDC), A. Argan, A. Trois, G. De Paris, V. Vittorini, F. D'Ammando, E. Costa, I. Donnarumma, M. Feroci, L. Pacciani, E. Del Monte, F. Lazzarotto, P. Soffitta, Y. Evangelista, I. Lapshov (INAF-IASF-Rm), A. Chen, A. Giuliani(INAF-IASF-Milano), M. Marisaldi, G. Di Cocco, C. Labanti, F. Fuschino, M. Galli (INAF/IASF Bologna), P. Caraveo, S. Mereghetti, F. Perotti (INAF/IASF Milano), G. Pucella, M. Rapisarda (ENEA-Roma), S. Vercellone (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, S. Colafrancesco, (ASDC), L. Salotti (ASI)
on 10 May 2010; 18:38 UT
Distributed as an Instant Email Notice (Transients)
Password Certification: Marco Tavani (

Subjects: X-ray, Gamma Ray, Black Holes, Neutron Stars, Transients
Referred to by ATEL #: 2611, 2644, 2646

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

Integrating during the period 2010-05-07 14:53 UT to 2010-05-09 17:19 UT (MJD= 55323.6-55325.7) the AGILE-GRID detected gamma-ray emission above 100 MeV from a source at Galactic coordinates (l,b) = (79.1,1.1) +/- 0.8 (stat.) +/- 0.1 (syst.) deg, and flux F > 100 e-8 ph/cm2/sec above 100 MeV (2-day significance in spinning mode above 3.5 sigma).

We notice that the hard X-ray lightcurve of Cyg X-3 as monitored by the BAT/Swift instrument (public data available at http:/// shows an overall decreasing trend starting on approximately MJD = 55311. A local minimum was reached on May 9th, 2010 (MJD=55325) in coincidence with the AGILE-GRID detection. This trend of decreasing hard X-ray emission in conjunction with gamma-ray flaring activity of Cyg X-3 was already detected in June, 2009.

We strongly encourage multifrequency observations of Cyg X-3.

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R. E. Rutledge , Editor
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