AGILE detection of the high Galactic latitude transient gamma-ray source AGL J0229+2054

ATel #1641; A. Bulgarelli (INAF/IASF Bologna), M. Tavani, G. Pucella, F. D'Ammando, V. Vittorini, G. Piano, 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, A. Rubini, (INAF/IASF Roma), F. Gianotti, M. Trifoglio, G. Di Cocco, C. Labanti, F. Fuschino, M. Marisaldi, E. Morelli, M. Galli (INAF/IASF Bologna), A. Chen, P. Caraveo, A. Giuliani, S. Mereghetti, A. Pellizzoni, S. Vercellone, F. Perotti, F. Fornari, M. Fiorini, A. Zambra (INAF/IASF Milano), 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), C. Pittori, F. Verrecchia, D. Gasparrini, P. Santolamazza, S. Colafrancesco, P. Giommi (ASDC) and L. Salotti (ASI)
on 1 Aug 2008; 15:24 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Marco Tavani (tavani@iasf-roma.inaf.it)

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During the current AGILE pointing centered at Galactic coordinates l = 134.7, b = -23.1, the Gamma-Ray Imaging Detector (GRID) discovered a fast variable gamma-ray source at high Galactic latitude.

Integrating from 2008-07-30 15:34 UT to 2008-07-31 15:23, a maximum likelihood analysis shows a detection at a significance level above 5 sigma, with a source flux in excess of about 100e-8 ph/cm2/s for photon energies larger than 100 MeV.

The source positional error box is centered at Galactic coordinates l = 151.7 deg, b = -36.4 deg (R.A. = 02h 29m 33s, DEC = +20d 54m 47s) and has a preliminary 95% confidence radius of about 1 degree. We name this source AGL J0229+2054. A preliminary analysis of the Super-AGILE data during the same time period and in the same sky region does not show any hard X-ray counterpart in the 20-60 keV energy range, with a 3-sigma upper limit of 30 mCrab on the average flux.

We note that the source is now under the AGILE-GRID detection threshold, implying a strong variability above 100 MeV on short time-scales.

We notice the presence at approximately 22' from the GRID error box centroid of a 100 mJy radio source at 5 GHz (CRATES J023030+211241). In addition, we notice the presence near the AGILE-GRID error box of the prominent blazar 1ES 0229+200, at a position approximately 61.3' from the GRID error box centroid.

The AGILE monitoring of the field including this source will continue until 2008-08-15 12:00 UT. We strongly encourage multi-frequency observations of the AGL J0229+2054 field, and in particular of the blazar 1ES 0229+200 and of the source CRATES J023030+211241.