PSR J1829 + 2456 is a radio pulsar in a relativistic binary system with another neutron star .
It has a rotational period of 41 ms and a mildly eccentric ( e = 0.14 ) 28-hr orbit .
We have continued its observations with the Arecibo radio telescope and have now measured the individual neutron star masses of this system .
We find the pulsar and companion masses to be 1.295 \pm 0.011 M _ { \odot } and 1.310 \pm 0.011 M _ { \odot } ( 2 \sigma - 95 \% confidence , unless stated otherwise ) , respectively .
We have also measured the proper motion for this system and used it to estimate its space velocity to be 46 ^ { +72 } _ { -30 } km s ^ { -1 } with respect to the local standard of rest .
Compared with the DNS population of measured masses , the relatively low values for companion mass , space velocity and orbital eccentricity in this system imply a similar binary evolution to that of other close double neutron star systems in which the ( second-formed ) companion is theorised to have been formed out of a low-kick , low mass-loss , symmetric supernova .