Persistent Emission Properties of SGR J1935+2154 During Its 2020 Active Episode

Abstract

We present detailed spectral and temporal characteristics of the persistent X-ray emission of SGR J1935+2154 based on our XMM-Newton and Chandra observations taken in the aftermath of its April 2020 burst storm, during which hundreds of energetic X-ray bursts were emitted, including one associated with an extraordinary fast radio burst. We clearly detect the pulsed X-ray emission in the XMM-Newton data. An average spin-down rate of 1.6$\times$10${}^{-11}$ s s${}^{-1}$ is obtained using our spin period measurement combined with three earlier values reported from the same active episode. Our investigations of the XMM-Newton and Chandra spectra with a variety of phenomenological and physically-motivated models, concluded that the magnetic field topology of SGR J1935+2154 is most likely highly non-dipolar. The spectral models indicate that surface field strengths in somewhat localized regions substantially exceed the polar value of 4.4$\times$10${}^{14}$ G inferred from a spin-down torque associated with a rotating magnetic dipole.

arXiv commentAccepted for publication in the ApJ Letters

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• Discovery of the linear energy-dependence of the spectral lag of X-ray bursts from SGR J1935+2154
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• Multipolar Electromagnetic Emission of Newborn Magnetar
• Retuning radio astronomy for axion dark matter with neutron stars
• Prompt and Afterglow Constraints on the Central Engine of GRB 240825A
• About the observational check of the mechanism of gamma radiation in Soft Gamma Repeaters (SGR)
• A month of monitoring the new magnetar Swift J1555.2-5402 during an X-ray outburst