TITLE: GCN CIRCULAR NUMBER: 9524 SUBJECT: GRB 090618: AGILE observations DATE: 09/06/18 15:21:44 GMT FROM: Marco Feroci at IASF/INAF F. Longo, E. Moretti, G. Barbiellini, E. Vallazza (INFN Trieste), M.Trifoglio, A. Bulgarelli, F. Gianotti F. Fuschino, M. Marisaldi, C.Labanti, M.Galli, G.DiCocco (INAF/IASF Bologna), S. Cutini, C. Pittori (ASDC), M.Tavani, E.Striani, G. Pucella, F. D'Ammando, V.Vittorini, A. Argan, A. Trois, G. Piano, S. Sabatini (INAF/IASF Rome), E. Del Monte, M. Feroci, Y. Evangelista, I. Donnarumma, L. Pacciani, P. Soffitta, E. Costa, F.Lazzarotto, I. Lapshov, M. Rapisarda (INAF/IASF Rome) A. Giuliani, A. Chen, S. Mereghetti, F. Perotti, P. Caraveo (INAF/IASF Milano), A. Pellizzoni, M. Pilia (INAF/OA Cagliari), S. Vercellone (INAF/IASF Palermo), P. Picozza, A. Morselli (INFN Roma-2), M. Prest (Universita` dell'Insubria), P. Lipari, D. Zanello (INFN Roma-1), A. Rappoldi, P. Cattaneo (INFN Pavia) and P. Giommi, P. Santolamazza, F. Verrecchia (ASDC) and L. Salotti (ASI), on behalf of the AGILE Team, report: The AGILE satellite detected GRB 090618 (P. Schady et al. GCN #9512) at about 36 degrees off axis. Super-AGILE, operating in the 18-60 keV energy range, triggered and localized the burst in the 1-D region of the field of view at a position consistent with the Swift/BAT localization. The emission from this bright GRB with a complex lightcurve was detected at high significance despite the large off-axis direction. AGILE-MCAL, operating in the 350 keV - 100 MeV energy range, triggered this GRB at 08:28:24.772 UT (T0). The MCAL overall burst duration is about 100 sec. The burst is composed by three main pulses, the brightest starting at T0+62sec and lasting about 14 seconds. The total MCAL spectrum between T0 and T0+120 sec can be fit by a simple powerlaw with photon index 3.16 (-0.30, +0.39) (90% c.l.), with reduced chi^2 0.99 (9 d.o.f.), in the 0.5-10 MeV energy range. The estimated fluence is (3.2 +/- 0.6) 10^{-5} erg cm^-2 in the same energy range. From a preliminary analysis of the AGILE-GRID data in the energy range 30 MeV-30 GeV no significant gamma-ray emission above 30 MeV is detected in the GRB error box during both the first and second main pulse for a total duration of about 130 sec. A preliminary upper limit is 0.1 ph cm^-2 over a 130 s duration. GRB 090618 provides a clear evidence for a class of GRBs bright below a few MeV, showing the lack of significant gamma-ray emission above 30 MeV.