Abstract
Magnetars are slowly rotating neutron stars that possess the strongest magnetic fields known in the cosmos (1014 − 1015 G). They display a range of transient high-energy electromagnetic activity. The brightest and most energetic of these events are the gamma-ray bursts (GRBs) known as magnetar giant flares (MGFs), with isotropic energies Eiso ≈ 1044 − 1046 erg. Only seven MGF detections have been made to date: three unambiguous events occurred in our Galaxy and the Magellanic Clouds, and the other four MGF candidates are associated with nearby star-forming galaxies. As all seven identified MGFs are bright at Earth, additional weaker events likely remain unidentified in archival data. We conducted a search of the Fermi Gamma-ray Burst Monitor database for candidate extragalactic MGFs and, when possible, collected localization data from the Interplanetary Network (IPN) satellites. Our search yielded one convincing event, GRB 180128A. IPN localizes this burst within NGC 253, commonly known as the Sculptor Galaxy. The event is the second MGF in modern astronomy to be associated with this galaxy and the first time two bursts have been associated with a single galaxy outside our own. Here we detail the archival search criteria that uncovered this event and its spectral and temporal properties, which are consistent with expectations for a MGF. We also discuss the theoretical implications and finer burst structures resolved from various binning methods. Our analysis provides observational evidence of an eighth identified MGF.
Funder
NASA
Department of Energy
Commissariat `a l’Energie Atomique
Centre National de la Recherche Scientifique / Institut National de Physique Nucl ́eaire et de Physique des Particules
Agenzia Spaziale Italiana
Istituto Nazionale di Fisica Nucleare
Ministry of Education, Culture, Sports, Science and Technology
High Energy Accelerator Research Organization
Japan Aerospace Exploration Agency
K. A. Wallenberg Foundation,
The Swedish Research Council
The Swedish National Space Board
Lomonosov MSU development program
Cited by
1 articles.
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