Binary evolution of PSR J1713+0747

Abstract

PSR J1713+0747 is a binary millisecond radio pulsar with a long orbital period (Porb ∼ 68 d) and a very low neutron star mass (M NS = 1.3 ± 0.2 M⊙). We simulate the evolution of this binary system with an accurate numerical code, which keeps into account both the evolution of the primary and of the whole binary system. We show that strong ejection of matter from the system is fundamental to obtain a mass at the end of the evolution that is within 1 - σ from the observed one, but propeller effects are almost negligible in such a system, where the accretion rate is always near to the Eddington limit. We show that there are indeed two mechanisms can account for the amount of mass loss from the system: 1) Radio ejection could be triggered due to a contraction of the donor, and could account for a significant loss of mass 2) Disc instabilities can occur, and can trigger strongly super-Eddington mass transfer phases resulting in a large amount of mass lost from the system. We argue that the same mechanisms could be important in other large period binaries