Study on the X-Ray Re-brightening Signature of GRB 220117A

Abstract

Abstract The Swift/XRT detected the X-ray afterglow of long burst GRB 220117A, which began to rebrighten 300 s after triggering and followed a single power-law decay segment after thousands of seconds of the orbital observation gap. This segment is different from the shallow decay segment (plateau) and flare, and may belong to a giant X-ray bump. We investigated this segment by the fall-back accretion model and found that the model can interpret this segment with reasonable parameter values. Within this physical model scenario, the fall-back accretion rate reaches a peak value ∼1.70 × 10−5 M ⊙ s−1 around 300 s in the central engine frame, which is compatible with the late mass supply rate of some low-metallicity massive progenitor stars. The initial black hole (BH) spin is a 0 = 0.64 − 0.26 + 0.24 and implies that this re-brightening signature requires a larger BH spin. The total accretion mass during the fall-back process is M acc = (3.09 ± 0.02) × 10−2 M ⊙. The jet energy from the fall-back accretion is (9.77 ± 0.65) × 1052 erg, with a ratio of 0.066 to the isotropic-equivalent radiation energies of the GRB prompt phase in the 1–104 keV band. The fall-back radius r p corresponding to the peak time of fall-back t p is (3.16 ± 0.05) × 1010 cm, which is consistent with the typical radius of Wolf–Rayet stars. In summary, our results provide additional support for the origin of the long burst from the core collapse of Wolf–Rayet stars, and its late central engine activity is likely due to the fall-back accretion process.