Compact Binary Mergers and the Event Rate of Fast Radio Bursts

• Published in: The Astrophysical journal 2018-05, Vol.858 (2), p.89
• Main Authors: Cao, Xiao-Feng, Yu, Yun-Wei, Zhou, Xia
• Format: Article
• Language: English
• Subjects: Astrophysics; Binary stars; Black holes; Delay time; Deposition; Electric power distribution; Neutron stars; Power law; Radiation; Radio bursts; radio continuum: general; Red shift; Sky surveys (astronomy); Star & galaxy formation; Star formation; stars: neutron; Time lag; White dwarf stars; white dwarfs
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/aabadd

Fast radio bursts (FRBs) are usually suggested to be associated with mergers of compact binaries consisting of white dwarfs (WDs), neutron stars (NSs), or black holes (BHs). We test these models by fitting the observational distributions in both redshift and isotropic energy of 22 Parkes FRBs, where, as usual, the rates of compact binary mergers (CBMs) are connected with cosmic star formation rates by a power-law distributed time delay. It is found that the observational distributions can well be produced by the CBM model with a characteristic delay time from several tens to several hundreds of megayears and an energy function index 1.2 γ 1.7, where a tentative fixed spectral index β = 0.8 is adopted for all FRBs. Correspondingly, the local event rate of FRBs is constrained to for an adopted minimum FRB energy of Emin = 3 × 1039 erg, where fb is the beaming factor of the radiation, is the duration of each pointing observation, and is the sky area of the survey. This event rate, about an order of magnitude higher than the rates of NS-NS/NS-BH mergers, indicates that the most promising origin of FRBs in the CBM scenario could be mergers of WD-WD binaries. Here a massive WD could be produced since no FRB was found to be associated with an SN Ia. Alternatively, if all FRBs can repeat on a timescale much longer than the period of current observations, then they could also originate from a young active NS that forms from relatively rare NS-NS mergers and accretion-induced collapses of WD-WD binaries.