PSR J2150+3427: A Possible Double Neutron Star System

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 omega(center dot) = 0.0115(4) deg yr(-1). An estimate for the total mass of the system using the omega(center dot) gives M-tot = 2.59(13)M-circle dot, 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 omega(center dot) with the mass function of the system gives the masses of M-p < 1.67 and M-c > 0.98 M-circle dot 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 omega(center dot), 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 omega(center dot) = 5.07(6) x 10(29) erg s(-1), PSR J2150+3427 is a very low-luminosity pulsar, with only the binary pulsar J2208+4610 having a smaller omega(center dot).