Central Engine Memory of Gamma-Ray Bursts and Soft Gamma-Ray Repeaters

Abstract

Gamma-ray Bursts (GRBs) are bursts of $\gamma$-rays generated from relativistic jets launched from catastrophic events such as massive star core collapse or binary compact star coalescence. Previous studies suggested that GRB emission is erratic, with no noticeable memory in the central engine. Here we report a discovery that similar light curve patterns exist within individual bursts for at least some GRBs. Applying the Dynamic Time Warping (DTW) method, we show that similarity of light curve patterns between pulses of a single burst or between the light curves of a GRB and its X-ray flare can be identified. This suggests that the central engine of at least some GRBs carries "memory" of its activities. We also show that the same technique can identify memory-like emission episodes in the flaring emission in Soft Gamma-Ray Repeaters (SGRs), which are believed to be Galactic, highly magnetized neutron stars named magnetars. Such a phenomenon challenges the standard black hole central engine models for GRBs, and suggest a common physical mechanism behind GRBs and SGRs, which points towards a magnetar central engine of GRBs.

7 pages, 4 figures, ApJ Letters in press

References in corpus (8)

• The Physics of Gamma-Ray Bursts and Relativistic Jets
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• The First Survey of X-ray Flares from Gamma Ray Bursts Observed by Swift: Temporal Properties and Morphology
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• Steep Decay Phase Shaped by the Curvature Effect. II. Spectral Evolution
• Unveil A Peculiar Light Curve Pattern of Magnetar Burst with GECAM observations of SGR J1935+2154
• GRB 201104A: A "Repetitive" Short Gamma-Ray Burst?
• A lower occurrence rate of bright X-ray flares in SN-GRBs than $z<1$ GRBs: evidence of energy partitions?