GRB 201223A: Implication of Fallback Accretion onto the Newborn Black Hole from its Multiband Afterglow 后印本

摘要: Multiband afterglow observations of gamma-ray bursts (GRBs) are important for studying the central engine. GRB 201223A is a GRB with prompt optical detection by GWAC. Here we report on the early optical afterglow of GRB 201223A detected by NEXT (only 2.8 minutes after the Swift/BAT trigger), which smoothly connects the prompt optical emission and the afterglow phase. Utilizing Amati diagrams and considering the detection of afterglow emission in the Swift u-band, we suggest a redshift range of 0.26–1.85. Based on our optical data and combined with early optical observation from GWAC and early X-ray data from Swift/XRT, a multiband fitting is performed using PyFRS, and we obtain the best afterglow parameters (assuming a redshift of z=1.0):  erg, ,  deg,  cm−3, , , . The late-time X-ray shows a re-brightening, indicating late-time central engine activities. After comparing the leading two central engine models, i.e., magnetar model and hyperaccreting black hole model, we find that the fallback accretion onto a newborn black hole provides a better explanation for the X-ray re-brightening with fallback accretion rate  and the total fallback accreted mass Mfb ≃ 1.41 × 10−6M⊙.