[ Previous | Next | ADS ]

AGILE detection of the flaring gamma-ray source AGL2021+4029: a possible rebrightening of a strong source in the Cygnus region

ATel #1585; A. Chen, P. Caraveo, A. Giuliani, 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, E. Vallazza (INFN Trieste), P. Picozza, A. Morselli (INFN Roma-2), M. Prest (Universita` dell'Insubria), P. Lipari, D. Zanello (INFN Roma-1), P. Cattaneo (INFN Pavia) and C. Pittori, F. Verrecchia, B. Preger, P. Santolamazza, P. Giommi
on 23 Jun 2008; 17:31 UT
Credential Certification: Andrew Chen (chen@iasf-milano.inaf.it)

Subjects: Gamma Ray, >GeV, Transient, Variables

Referred to by ATel #: 1589, 1595, 1597, 1623, 1848

Integrating from 2007-11-02 12:00 UT to 2008-05-01 00:00, AGILE-GRID (Gamma-Ray Imaging Detector) detects a gamma-ray point source above 19 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 = 78.31 deg, b = 2.05 deg, and has a radius of about 0.25 degrees. The nearest EGRET source is 3EG J2020+4017 at (l,b) = (78.05,2.08) with an error radius of 0.16 degrees.

The position of this source is consistent with the transient sources previously reported in ATel #1492 and #1547. We note that although the flux reported in #1492 is significantly higher than the mean integrated flux, the flux during the #1547 is consistent with the mean value. We also note that the position of the proposed counterpart IGR J20187+4041 = 2MASX J20183871+4041003 (ATel #1497, #1498, #1518, #1584) lies OUTSIDE the 95% source location contour of the integrated source.

While pointing at the Cygnus region, AGILE detected renewed gamma-ray emission consistent with this source, beginning on 2008-06-20 UT. A preliminary maximum likelihood analysis of the gamma-ray data obtained between 2008-06-20 16:30 UT and 2008-06-21 16:30 UT for photon energies above 100 MeV results in a detection significance of about 4.9 sigma, with a source flux in excess of 200e-8 ph/cm2/s at energies above 100 MeV, two standard deviations higher than the mean flux of the integrated source. The source positional error box is centered at Galactic coordinates l = 78.6 deg, b = 1.7 deg, and has a radius of about 0.6 degrees. We note that the position is consistent with the integrated source, while 2MASX J20183871+4041003 lies outside 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 20 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, concentrating on the error box of the persistent source.