Gravitational wave GW170817: A new-born sub-millisecond pulsar and the properties of coalescing double neutron stars

Abstract The gravitational wave event GW170817 is ascribed to the coalescence of a double neutron star (DNS) based on the multi-messenger observations. Based on the detected gravitational wave frequency by LIGO and the afterglow observations by the optical and Gamma-ray instruments, it is inferred that the outcome of coalescence kilonova of GW170817 is most probably the birth of a fast rotating sub-millisecond pulsar (SMSP), with the spin frequency of  ∼ 1490 Hz (period of P ∼ 0.67 ms), and magnetic field of B ∼ 10 11 − 15  G depending on the magnetic reconstruction process of the new NS. The mass and radius of this new born SMSP is estimated to be about  ∼ 2.6M ⊙ and 12 − 25  km, respectively, then the EOS and nuclear composition of such a super-spinning and massive compact object is still open, after comparing with the predictions of the known EOS models. The observations of this new type of SMSP after GW170817 is proposed, and its extreme properties are investigated, for instance, its magnetic dipole spin-down induced energy dissipation rate is E ˙ ∼ 10 44 ( B / 10 12 G ) 2  erg/s, which is four orders of magnitudes more luminous than that of Crab pulsar, and accordingly its spin-down characteristic age is as short as 30 years. While considering the distance of the source at 130 million light years, the corresponding energy dissipation rate is E ˙ ∼ 10 35 ( B / 10 12 G ) 2  erg/s at the location of Crab pulsar, which could be observed by sensitive X, gamma and radio telescopes if this pulsar sweeps its radiation beam across the Earth.