http://arxiv.org/abs/2205.05031
Recently, a Kilonova-associated gamma-ray burst (GRB 211211A) has attracted great attentions, whose lightcurve consists a precursor ($\sim 0.2$ s), a hard spiky emission ($\sim 10$ s), and a soft long extended emission ($\sim 40$ s). Kilonova association could prove its merger origin, while the detection of the precursor infers at least one highly magnetized NS being involved in the merger. In this case, a strong magnetic flux $\Phi$ is expected to surround the central engine of GRB 211211A. Here we suggest that when $\Phi$ is large enough, the accretion flow could be halted far from the innermost stable radius, which will significantly prolong the lifetime of the accretion process, so as the GRB duration. For example, we show that as long as the central BH is surrounded by a strong magnetic flux $\Phi\sim 10^{29}\rm cm^2 G$, an accretion flow with $\dot{M}{\rm ini} \simeq 0.1 M\odot s^{-1}$ could be halted at 40 times gravitational radius and slowly transfer into the black hole in order of $\sim$10 s, which naturally explains the duration of hard spiky emission. After most of the disk mass has been accreted onto the BH, the inflow rate will be reduced, so a long and soft extended emission is expected when a new balance between the magnetic field and the accretion current is reconstructed at a further radius. Our results further support that the special behavior of GRB 211211A is mainly due to the strong magnetic field of its progenitor stars. Multi-messenger detections of GRB 211211A-like events (sometimes may disguise as a typical LGRBs without extended emission) could help to diagnose their progenitor system and to better study the events of compact binary mergers involving high magnetic field NSs.
H. Gao, W. Lei and Z. Zhu
Wed, 11 May 22
22/60
Comments: 5 pages, 1 figure