AGILE detection of a gamma ray flare from the Cygnus X-1 region

ATel #2512; A. Bulgarelli (INAF/IASF-Bo), C. Pittori, F. Lucarelli (ASDC), E. Striani (Univ. Roma Tor Vergata and INFN Roma), F. Gianotti, M. Trifoglio (INAF/IASF-Bo), S. Sabatini, M. Tavani (INAF/IASF-Rm, and Univ. Tor Vergata), F. Verrecchia (ASDC), A. Trois (INAF/IASF-Rm), A. Chen, A. Giuliani, S. Mereghetti, P. Caraveo, F. Perotti (INAF/IASF-Mi), S. Vercellone, F. D'Ammando (INAF/IASF-Pa), I. Donnarumma, E. Del Monte, Y. Evangelista, M. Feroci, F. Lazzarotto, L. Pacciani, P. Soffitta, E. Costa, I. Lapshov, M. Rapisarda, A. Argan, G. Piano, G. Pucella, V. Vittorini (INAF/IASF-Rm), F. Fuschino, M. Galli, C. Labanti, M. Marisaldi, G. Di Cocco (INAF/IASF-Bo), A. Pellizzoni, M. Pilia (INAF/OA-Cagliari), G. Barbiellini, F. Longo, E. Moretti, E. Vallazza (INFN Trieste), A. Morselli, P. Picozza (INFN and Univ. Roma Tor Vergata), M. Prest (Universita` dell'Insubria), P. Lipari, D. Zanello (INFN and Univ. Roma Sapienza), P. W. Cattaneo, A. Rappoldi (INFN Pavia), P. Santolamazza, S. Colafrancesco, P. Giommi (ASDC) and L. Salotti (ASI)
on 25 Mar 2010; 17:22 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Sabina Sabatini (sabina.sabatini@iasf-roma.inaf.it)

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AGILE is detecting an intense gamma-ray emission above 100 MeV from a source of Galactic coordinates (l, b) = (70.3 2.5) ± 1.2 deg (95% stat. c.l. and systematic error) (1-day integration).

Integrating from 2010-03-24 02:24 UT to 2010-03-25 01:01 UT, a maximum likelihood analysis yields a detection at a significance level of about 5 sigma, and a flux above 250 10-8 ph/cm2/s (E > 100 MeV). For a 2-days integration (2010-03-23 05:05 UT to 2010-03-25 04:25 UT) a maximum likelihood analysis yields a detection of 3.7 sigma with a flux of (200 ± 90) 10-8 ph/cm2/s for E > 100 MeV.

We note that the black-hole binary Cygnus X-1 and 1FGLJ1958.9+3459 are within the source error box.

These measurements were obtained with AGILE observing a large portion of the sky in a spinning mode.

Multifrequency observations of the Cygnus X-1 region are strongly encouraged.