High-energy emission from a magnetar giant flare in the Sculptor galaxy

Ajello M, Atwood WB, Axelsson M, Baldini L, Barbiellini G, Baring MG, Bastieri D, Bellazzini R, Berretta A, Bissaldi E, Blandford RD, Bonino R, Bregeon J, Bruel P, Buehler R, Burns E, Buson S, Cameron RA, Caraveo PA, Cavazzuti E, Chen S, Cheung CC, Chiaro G, Ciprini S, Costantin D, Crnogorcevic M, Cutini S, D'Ammando F, De La Torre Luque P, De Palma F, Digel SW, Di Lalla N, Di Venere L, Dirirsa FF, Fukazawa Y, Funk S, Fusco P, Gargano F, Giglietto N, Gill R, Giordano F, Giroletti M, Granot J, Green D, Grenier IA, Griffin S, Guiriec S, Hays E, Horan D, Johannesson G, Kerr M, Kovacevic M, Kuss M, Larsson S, Latronico L, Li J, Longo F, Loparco F, Lovellette MN, Lubrano P, Maldera S, Manfreda A, Marti-Devesa G, Mazziotta MN, Mcenery JE, Mereu I, Michelson PF, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Negro M, Omodei N, Orienti M, Orlando E, Paliya VS, Paneque D, Pei Z, Pesce-Rollins M, Piron F, Poon H, Porter TA, Principe G, Racusin JL, Raino S, Rando R, Rani B, Razzaque S, Reimer A, Reimer O, Parkinson PMS, Scargle JD, Scotton L, Serini D, Sgro C, Siskind EJ, Spandre G, Spinelli P, Tajima H, Takahashi MN, Tak D, Torres DF, Tosti G, Troja E, Wadiasingh Z, Wood K, Yassine M, Yusafzai A, Zaharijas G (2021)

Publication Type: Journal article

Publication year: 2021


DOI: 10.1038/s41550-020-01287-8


Magnetars are the most highly magnetized neutron stars in the cosmos (with magnetic field 10(13)-10(15) G). Giant flares from magnetars are rare, short-duration (about 0.1 s) bursts of hard X-rays and soft gamma rays(1,2). Owing to the limited sensitivity and energy coverage of previous telescopes, no magnetar giant flare has been detected at gigaelectronvolt (GeV) energies. Here, we report the discovery of GeV emission from a magnetar giant flare on 15 April 2020 (refs. (3,4) and A. J. Castro-Tirado et al., manuscript in preparation). The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected GeV gamma rays from 19 s until 284 s after the initial detection of a signal in the megaelectronvolt (MeV) band. Our analysis shows that these gamma rays are spatially associated with the nearby (3.5 megaparsecs) Sculptor galaxy and are unlikely to originate from a cosmological gamma-ray burst. Thus, we infer that the gamma rays originated with the magnetar giant flare in Sculptor. We suggest that the GeV signal is generated by an ultra-relativistic outflow that first radiates the prompt MeV-band photons, and then deposits its energy far from the stellar magnetosphere. After a propagation delay, the outflow interacts with environmental gas and produces shock waves that accelerate electrons to very high energies; these electrons then emit GeV gamma rays as optically thin synchrotron radiation. This observation implies that a relativistic outflow is associated with the magnetar giant flare, and suggests the possibility that magnetars can power some short gamma-ray bursts.

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Involved external institutions

Clemson University US United States (USA) (US) University of California Santa Cruz US United States (USA) (US) Stockholm University / Stockholms universitet SE Sweden (SE) University of Pisa / Università di Pisa (UniPi) IT Italy (IT) National Institute for Nuclear Physics / Istituto Nazionale di Fisica Nucleare (INFN) IT Italy (IT) Rice University US United States (USA) (US) Università degli Studi di Perugia IT Italy (IT) Politecnico di Bari IT Italy (IT) Stanford University US United States (USA) (US) University of Montpellier / Université Montpellier FR France (FR) École Polytechnique - Université Paris-Saclay FR France (FR) Deutsches Elektronen-Synchrotron DESY DE Germany (DE) Louisiana State University US United States (USA) (US) Julius-Maximilians-Universität Würzburg DE Germany (DE) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) IT Italy (IT) Italian Space Agency / Agenzia Spaziale Italiana (ASI) IT Italy (IT) U.S. Naval Research Laboratory US United States (USA) (US) University of Padua / Universita degli Studi di Padova IT Italy (IT) University of Maryland US United States (USA) (US) Hiroshima University JP Japan (JP) George Washington University (GWU) US United States (USA) (US) Open University of Israel / האוניברסיטה הפתוחה IL Israel (IL) Max-Planck-Institut für Physik (Werner-Heisenberg-Institut, MPP) / Max Planck Institute for Physics DE Germany (DE) University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot FR France (FR) National Aeronautics and Space Administration (NASA) US United States (USA) (US) University of Iceland (UI) / Háskóli Íslands IS Iceland (IS) Royal Institute of Technology / Kungliga Tekniska Högskolan (KTH) SE Sweden (SE) Leopold-Franzens-Universität Innsbruck / University of Innsbruck AT Austria (AT) University of Johannesburg ZA South Africa (ZA) NYCB Real-Time Computing, Inc. US United States (USA) (US) Institute of Space Sciences (IEEC-CSIC) ES Spain (ES) Praxis, Inc. US United States (USA) (US)

How to cite


Ajello, M., Atwood, W.B., Axelsson, M., Baldini, L., Barbiellini, G., Baring, M.G.,... Zaharijas, G. (2021). High-energy emission from a magnetar giant flare in the Sculptor galaxy. Nature Astronomy. https://doi.org/10.1038/s41550-020-01287-8


Ajello, M., et al. "High-energy emission from a magnetar giant flare in the Sculptor galaxy." Nature Astronomy (2021).

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