PSR J2150+3427: A Possible Double Neutron Star System

Abstract

PSR J2150+3427 is a 0.654 s pulsar discovered by the Commensal Radio Astronomy FAST Survey. From the follow-up observations, we find that the pulsar is in a highly eccentric orbit (e = 0.601) with an orbital period of 10.592 days and a projected semimajor axis of 25.488 lt-s. Using 2.7 yr of timing data, we also measured the rate of periastron advance ω ̇ = 0.0115(4) deg yr−1. An estimate for the total mass of the system using the ω ̇ gives M tot = 2.59(13)M ⊙, which is consistent with most of the known double neutron star (DNS) systems and one neutron star (NS)–white dwarf (WD) system named B2303+46. Combining ω ̇ with the mass function of the system gives the masses of M p < 1.67 and M c > 0.98 M ⊙ for the pulsar and the companion star, respectively. This constraint, along with the spin period and orbital parameters, suggests that it is possibly a DNS system, and we cannot entirely rule out the possibility of an NS–WD system. Future timing observations will vastly improve the uncertainty in ω ̇ , and are likely to allow the detection of additional relativistic effects, which can be used to modify the values of M p and M c . With a spin-down luminosity of E ̇ = 5.07(6) × 1029 erg s−1, PSR J2150+3427 is a very low-luminosity pulsar, with only the binary pulsar J2208+4610 having a smaller E ̇ .