Pulsar J1411+2551: A Low Mass New Double Neutron Star System

In this work, we report the discovery and characterization of PSR J1411+2551, a new binary pulsar discovered in the Arecibo 327 MHz Drift Pulsar Survey. Our timing observations of the radio pulsar in the system span a period of about 2.5 years. This timing campaign allowed a precise measurement of its spin period (62.4 ms) and its derivative (9.6 $\pm$ 0.7) $\times 10^{-20}, \rm s, s^{-1}$;fromthese,wederiveacharacteristicageof$\sim 10,$Gyr and a surface magnetic field strength of 2.5 $\times {10}^9$ G. These numbers indicate that this pulsar was mildly recycled by accretion of matter from the progenitor of the companion star. The system has an eccentric ($e=0.17$) 2.61 day orbit. This eccentricity allows a highly significant measurement of the rate of advance of periastron, $\dot{\omega} = 0.07686 \pm 0.00046 ^{\circ}~{\rm yr}^{-1}$. Assuming general relativity accurately models the orbital motion, this implies a total system mass M = $2.538 \pm 0.022 M_{\odot}$\mathrm{.}Theminimumcompanionmassis$0.92, M_{\odot}$ and the maximum pulsar mass is $1.62M_{\odot }$. The large companion mass and the orbital eccentricity suggest that PSR J1411+2551 is a double neutron star system; the lightest known to date including the DNS merger GW 170817. Furthermore, the relatively low orbital eccentricity and small proper motion limits suggest that the second supernova had a relatively small associated kick; this and the low system mass suggest that it was an ultra-stripped supernova.