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Rebrightening of the variable AGILE source in the Cygnus region

ATel #1547; A. Giuliani, P. Caraveo, A. Chen, S. Mereghetti, A. Pellizzoni, S. Vercellone, F. Perotti, F. Fornari, M. Fiorini, A. Zambra (INAF/IASF Milano), M. Tavani, G. Pucella, F. D'Ammando, V. Vittorini, E. Costa, M. Feroci, I. Donnarumma, L. Pacciani, E. Del Monte, F. Lazzarotto, P. Soffitta, Y. Evangelista, I. Lapshov, M. Rapisarda, A. Argan, A. Trois, G. De Paris (INAF/IASF Roma), A. Bulgarelli, F. Gianotti, M. Trifoglio, G. Di Cocco, C. Labanti, F. Fuschino, M. Marisaldi, M. Galli, (INAF/IASF Bologna), G. Barbiellini, F. Longo, (INFN Trieste), P. Picozza, A. Morselli (INFN Roma-2), M. Prest, E. Vallazza (Universita` dell'Insubria), P. Lipari, D. Zanello (INFN Roma-1), P. Cattaneo (INFN Pavia) and P. Giommi, C. Pittori, D. Gasparrini, S. Cutini, B. Preger, P. Santolamazza, F. Verrecchia (ASDC) and L. Salotti (ASI)
on 27 May 2008; 17:29 UT
Credential Certification: Andrew Chen (chen@iasf-milano.inaf.it)

Subjects: Gamma Ray, >GeV, Transient

Referred to by ATel #: 1584, 1585, 1589, 1595, 1597

While pointing at the Cygnus region, AGILE detected renewed gamma-ray emission from the transient gamma-ray source previously reported in ATel #1492, beginning on 2008-05-22 UT.

A preliminary maximum likelihood analysis of the AGILE-GRID (Gamma-Ray Imaging Detector) data obtained between 2008-05-22 06:00 UT and 2008-05-27 06:00 UT for photon energies above 100 MeV results in a detection significance of about 6 sigma, with a source flux in excess of 100e-8 ph/cm2/s at energies above 100 MeV. The source positional error box is centered at Galactic coordinates l = 77.9 deg, b = 2.6 deg, and has a radius of about 0.5 degrees. We note that the possible counterpart IGR J20187+4041 = 2MASX J20183871+4041003 (ATel #1497, #1498, #1518) lies within the 95% source location contour.

A preliminary analysis of the Super-AGILE data over the same time period and the same sky region does not show any counterpart in the 20-60 keV energy range, with a 3-sigma upper limit of 10 mCrab on the average flux.

We strongly encourage multi-frequency observations of the field of the gamma-ray source detected by AGILE in an active gamma-ray flaring state, including the possible counterpart IGR J20187+4041 = 2MASX J20183871+4041003.