On The Study Of The Origins Of Fast Radio Bursts

Fast radio bursts(FRBs)are intense GHz transients with intrinsic durations less than several milliseconds,and energy?1039erg.Many models have been proposed to explain FRBs.It was suggested that FRBs can be produced by a single neutron star(NS),such as giant pulses of young pulsars,giant flares of magnetars,and magnetic field shedding of collapsing neutron stars.Some compact binary mergers,specifically,mergers of double white dwarfs(WDs),of WD-NS,of WD-black hole(BH),of dou-ble NSs,NS-BH,or of double BHs could be responsible for FRBs.Besides,there are also other novel m odels,such as pulsar traveling though asteroid belt,super-conducting strings,and so on.We propose the model that the coalescence of primordial black holes(PBHs)bi-naries with equal mass M?1028g can emit luminous gigahertz(GHz)radio transient,which may be candidate sources for the observed fast radio bursts(FRB s),if at least one black hole holds appropriate amount of net electric charge Q.Using a dimensionless quantity for the charge q ?Q/(?)GM,our analyses infer that q?O(10-5)can explain the FRBs with released energy of order O(1039)ergs.With the current sample of FRBs and assuming a distribution of charge?(q)for all PBHs,we can deduce that its form is proportional to q-3.0±0.1 if PBHs are sources of the observed FRBs.Furthermore,with the proposed hypothetical scenario and by estimating the local event rate of FRBs,one derives a lower bound for the fraction of PBHs(at the mass of 1028g)against that of matter fPBH(1028g)?10?5 needed to explain the rate.With this inspiring estimate,we expect that future observations of FRBs can help to falsify their physical origins from the PBH binaries coalescences.In the future,the gravitational waves produced by mergers of small black holes can be detected by high frequency gravitational wave detectors.We believe that this work would be a useful addition to the current literature on multimessenger astronomy and cosmology.Fast radio bursts(FRBs)are intense radio transients whose physical origin remains unknown.Therefore,it is of crucial importance to use a model-independent method to obtain the energy function and cosmic formation rate directly from the observational data.Based on current samples of Parkes and ASKAP,we determine,for the first time,the energy function and formation rate of FRBs by using the Lynden-Bell C-method.The energy function derived from the Parkes sample is a broken power law,however it is a simple power law for the ASKAP sample.For Parkes sample,we derive the formation rate which is roughly consistent with the star formation rate up to z~1.7,with a local formation rate of ?(O)(?)(3.2±0.3)× 104 Gpc?3yr-1 above a detection threshold of 2 Jyms.For ASKAP sample,we find that the formation rate evolves much faster than the star formation rate up to z?0.7,namely p(z)(?)x(1+z)6.9+1.9,with a local formation rate of p(0)(?)(4.6±0.8)×103 Gpc-3yr-1 above a detection threshold of 51 Jyms.This might be a important clue for the physical origin of FRBs.