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 } s s ^ { -1 } ; from these , we derive a characteristic age of > 9.1 Gyr and a surface magnetic field strength of < 2.6 \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 } ~ { } { yr } ^ { -1 } .
Assuming general relativity accurately describes the orbital motion , this implies a total system mass M = 2.538 \pm 0.022 \mathrm { M _ { \Sun } } .
The minimum companion mass is 0.92 \mathrm { M _ { \Sun } } and the maximum pulsar mass is 1.62 \mathrm { M _ { \Sun } } .
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 .