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An X-ray burst from a magnetar enlightening the mechanism of fast radio bursts


Fast radio bursts (FRBs) are millisecond radio pulses originating from powerful enigmatic sources at extragalactic distances. Neutron stars with large magnetic fields (magnetars) have been considered as the sources powering the FRBs, but the connection requires further substantiation. Here we report the detection by the AGILE satellite on 28 April 2020 of an X-ray burst in temporal coincidence with a bright FRB-like radio burst from the Galactic magnetar SGR 1935+2154. The burst observed in the hard X-ray band (18–60 keV) lasted about 0.5 s, it is spectrally cut off above 80 keV and implies an isotropically emitted energy of about 1040 erg. This event demonstrates that a magnetar can produce X-ray bursts in coincidence with FRB-like radio bursts. It also suggests that FRBs associated with magnetars can emit X-ray bursts. We discuss SGR 1935+2154 in the context of FRBs with low–intermediate radio energies in the range 1038–1040 erg. Magnetars with magnetic fields B ≈ 1015 G may power these FRBs, and new data on the search for X-ray emission from FRBs are presented. We constrain the bursting X-ray energy of the nearby FRB 180916 to be less than 1046 erg, smaller than that observed in giant flares from Galactic magnetars.

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Fig. 1: AGILE detection of the ‘forest’ of X-ray bursts from SGR 1935+2154.
Fig. 2: Detection of the X-ray burst in temporal coincidence with the very intense radio burst from SGR 1935+2154.
Fig. 3: Isotropically emitted energies of radio bursts detected from FRBs versus their redshift-corrected intrinsic time widths of their emission.
Fig. 4: High-energy (X-ray and gamma-ray) 3σ flux upper limits as a function of integration timescales of observations obtained by AGILE, Swift and Chandra satellites in monitoring the nearby repeating FRB 180916.
Fig. 5: X-ray monitoring by Swift-XRT of the nearby repeating FRB 180916 (3 February 2020 to 7 September 2020) during its five-day active time intervals of expected radio bursting based on periodicity.

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Data availability

The data used in this investigation are available on demand at the helpdesk of the AGILE website: The data that support the plots within this paper are available from the corresponding author.


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AGILE is a space mission of the Italian Space Agency (ASI) developed and operated with the collaboration of INAF and INFN. The research was carried out with partial support by the ASI grants I/028/12/05 and ASI 2014-049-R.0. We acknowledge satellite operations at the ground station in Malindi (Kenya) and at AGILE mission operation centre in Fucino (Italy). We also acknowledge the scientific ground segment activities at the ASI Space Science Data Center. We thank the team of the Neil Gehrels Swift Observatory for assistance in supporting X-ray observations. We thank D. D. Frederiks for useful exchanges.

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M. Tavani wrote the manuscript together with C.C., F.V. and A.U. C.P., F. Lucarelli and F.V. oversaw the AGILE satellite data flow and pipelines at the ASI Space Science Data Center. A.B., N.P., A. Argan, V.F. and L.B. contributed to the SW management and AGILE instrument pipelines. M.P. and S.P. contributed to the analysis of X-ray data. G. Bernardi, G. Bianchi, M.P., A. Magro, G.N., G. Pupillo and G.S. contributed to the analysis of radio data at the Northern Cross. Other authors belong to the whole AGILE team that contributed to supporting the writing of the manuscript and providing technical information and cross-check.

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Correspondence to M. Tavani.

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Tavani, M., Casentini, C., Ursi, A. et al. An X-ray burst from a magnetar enlightening the mechanism of fast radio bursts. Nat Astron 5, 401–407 (2021).

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