http://arxiv.org/abs/2106.14172
During April and May 2020, SGR J1935+2154 emitted hundreds of short bursts and became one of the most prolific transient magnetars. At the onset of the active bursting period, a 130-s burst
forest", which included some bursts with peculiar time profiles, were observed with the $Fermi$/Gamma-ray Burst Monitor. In this paper, we present the results of time-resolved spectral analysis of this burstforest” episode, which occurred on April 27, 2020. We identify thermal spectral components prevalent during the entire 130-s episode; high-energy maxima appear during the photon flux peaks, which are modulated by the spin period of the source. Moreover, the evolution of the $\nu F_{\nu}$ spectral hardness (represented by $E_{\rm peak}$ or blackbody temperature) within the lightcurve peaks is anti-correlated with the pulse phases extrapolated from the pulsation observed within the persistent soft X-ray emission of the source six hours later. Throughout the episode, the emitting area of the high-energy (hotter) component is 1–2 orders of magnitude smaller than that for the low-energy component. We interpret this with a geometrical viewing angle scenario, inferring that the high-energy component likely originates from a low-altitude hotspot located within closed toroidal magnetic field lines.
Y. Kaneko, E. Gogus, M. Baring, et. al.
Tue, 29 Jun 21
38/101
Comments: 23 pages, 8 figures, 1 table (full version), accepted for publication in ApJL
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