Magnetars are neutron stars with X-ray and soft γ-ray outbursts thought to be powered by intense internal magnetic fields1. Like conventional neutron stars in the form of radio pulsars, magnetars exhibit ‘glitches’ during which angular momentum is believed to be transferred between the solid outer crust and the superfluid component of the inner crust2,3,4. The several hundred observed glitches in radio pulsars5,6 and magnetars7 have involved a sudden spin-up (increase in the angular velocity) of the star, presumably because the interior superfluid was rotating faster than the crust. Here we report X-ray timing observations of the magnetar 1E 2259+586 (ref. 8), which exhibited a clear ‘anti-glitch’—a sudden spin-down. We show that this event, like some previous magnetar spin-up glitches9, was accompanied by multiple X-ray radiative changes and a significant spin-down rate change. Such behaviour is not predicted by models of neutron star spin-down and, if of internal origin, is suggestive of differential rotation in the magnetar, supporting the need for a rethinking of glitch theory for all neutron stars10,11.
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V.M.K. acknowledges support from the Natural Sciences and Engineering Research Council of Canada Discovery Grant and the John C. Polanyi Award, from the Canadian Institute for Advanced Research, from Fonds de Recherche Nature et Technologies Québec, from the Canada Research Chairs Program, and from the Lorne Trottier Chair in Astrophysics and Cosmology. D.T. was supported by the Lorne Trottier Chair in Astrophysics and Cosmology and the Canadian Institute for Advanced Research. K.N.G. was supported by the Centre de Recherche en Astrophysique du Québec. We thank H. Medlin and J. Gelfand for help with the EVLA observation. We thank D. Eichler, B. Link, M. Lyutikov and C. Thompson for useful discussions. We acknowledge the use of public data from the Swift data archive.
The authors declare no competing financial interests.
This file contains Supplementary Text and Data, which includes 1) Observations and 2) a Supplementary Discussion, Supplementary Figure 1 and additional references. (PDF 251 kb)
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Archibald, R., Kaspi, V., Ng, CY. et al. An anti-glitch in a magnetar. Nature 497, 591–593 (2013). https://doi.org/10.1038/nature12159
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