AGILE detection of a hard X-ray burst in temporal coincidence with a radio burst from SGR 1935+2154

ATel #13686; M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), A. Ursi (INAF/IAPS), F. Verrecchia (SSDC and INAF/OAR), C. Casentini (INAF/IAPS), C. Pittori (SSDC and INAF/OAR), M. Pilia (INAF/OA-Cagliari), M. Cardillo, G. Piano (INAF/IAPS), A. Bulgarelli, V. Fioretti, N. Parmiggiani (INAF/IASF-Bo), F. Lucarelli (SSDC and INAF/OAR), I. Donnarumma (ASI), S. Vercellone (INAF/OA-Brera), F. Gianotti, M. Trifoglio (INAF/IASF-Bo), A. Giuliani, S. Mereghetti, P. Caraveo, F. Perotti (INAF/IASF-Mi), A. Chen (Wits University), A. Argan, E. Costa, E. Del Monte, Y. Evangelista, M. Feroci, F. Lazzarotto, I. Lapshov, L. Pacciani, P. Soffitta, V. Vittorini (INAF/IAPS), G. Di Cocco, F. Fuschino, M. Galli, C. Labanti (INAF/IASF-Bo), M. Marisaldi (INAF/OAS-Bologna, and Bergen University), A. Pellizzoni, A. Trois (INAF/OA-Cagliari), G. Barbiellini, E. Vallazza (INFN Trieste), F. Longo (Univ. Trieste and INFN Trieste), A. Morselli, P. Picozza (INFN and Univ. Roma Tor Vergata), M. Prest (Univ. dell'Insubria), P. Lipari, D. Zanello (INFN and Univ. Roma Sapienza), P. W. Cattaneo, A. Rappoldi (INFN Pavia), A. Ferrari (Univ. Torino and CIFS), F. Paoletti (East Windsor RSD Hightstown and INAF/IAPS), A. Antonelli (INAF/OAR), P. Giommi, L. Salotti, G. Valentini, and F. D'Amico (ASI)
on 29 Apr 2020; 11:05 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Francesco Verrecchia (francesco.verrecchia@asdc.asi.it)

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We checked AGILE data in coincidence with the radio burst reported by CHIME/FRB at T0 = 2020-04-28 14:34:33 UTC (topocentric arrival time at 400 MHz), emitted by SGR 1935+2154 (ATel #13681; Scholz et al.). The event position was accessible by the AGILE detectors and it was not occulted by the Earth for an off-axis angle of 121 deg. We considered ratemeter data for SuperAGILE (20-60 keV), the MiniCalorimeter (0.4-100 MeV), and the Anti-Coincidence (50-200 keV) detectors.

Yesterday, we detected several bursts from SGR 1935+2154 with the SuperAGILE and Anti-Coincidence detectors, as announced in the ATel #13682 (Ursi et al.). Regarding the radio burst at T0, we report here the weak detection of an X-ray event obtained by the SuperAGILE ratemeters (with a time resolution of 0.5 s).

The event occurs at T = 2020-04-28 14:34:24 UTC, lasts approximately 0.5 s, and it has a significance above 4 sigma over the background. We notice that the AGILE detection time corresponds to the de-despersed arrival topocentric time of the CHIME/FRB radio detection at infinite frequency. The event time is in agreement with the INTEGRAL/IBAS detection (GCN #27668, Mereghetti et al.).

We therefore attribute this event to the SGR 1935+2154, simultaneously emitting radio and hard X-ray emission. From the lack of detection of Anti-Coincidence and MiniCALorimeter detectors, we deduce that the spectrum of this event is relatively soft.

The SuperAGILE ratemeter light curve can be found at http://www.agilescienceapp.it/notices/SuperAGILE_SGR1935+2154.png .
Additional analysis of the AGILE data is in progress.