Repeating FRB from the Pulsar-asteroid Belt Collision : Frequency Drifting and Polarization

Liu, Zenan

Fast radio bursts (FRBs) are a new kind of extragalactic radio transients. Some of them appear repeating behaviors. Recent observations show that some repeating FRBs, e.g, FRB 121102, presented time--frequency downward drifting patterns and the nearly 100$\%$ linear polarization. Following the model of \citet{dai 2016} that proposed that some repeating FRBs may origin from a slow spinning pulsar colliding with the asteroid belt around, we focused on the prediction of time--frequency drifting and polarization in this model.
In this scenario, the frequency drifting is mainly caused by the geometric structure of a pulsar magnetosphere, and the drifting rate--frequency index is proposed to be 25/17. On the other hand, by involving the mass distribution of the incident asteroids, we find that an asteroid with mass of $m\gtrsim 10^{17}~{\rm g}$ colliding with the pulsar would contribute abundant gravitational energy and generate  FRBs. Since the mass difference of the incident asteroids, a broad frequency band of FRBs would be expected. Furthermore, we simulate the linear polarization distribution for these repeating FRBs, and constrain the linear polarization with $\gtrsim$ 30$\%$ for the FRBs with flux an order of magnitude lower than the maximum flux.