We report the discovery of PSR J1906+0746 , a young 144-ms pulsar in a highly relativistic 3.98-hr orbit with an eccentricity of 0.085 and expected gravitational wave coalescence time of \sim 300 Myr .
The new pulsar was found during precursor survey observations with the Arecibo 1.4-GHz feed array system and retrospectively detected in the Parkes Multibeam plane pulsar survey data .
From radio follow-up observations with Arecibo , Jodrell Bank , Green Bank , and Parkes , we have measured the spin-down and binary parameters of the pulsar and its basic spectral and polarization properties .
We also present evidence for pulse profile evolution , which is likely due to geodetic precession , a relativistic effect caused by the misalignment of the pulsar spin and total angular momentum vectors .
Our measurements show that PSR J1906+0746 is a young object with a characteristic age of 112 kyr .
From the measured rate of orbital periastron advance ( 7.57 \pm 0.03 ° yr ^ { -1 } ) , we infer a total system mass of 2.61 \pm 0.02 M _ { \odot } .
While these parameters suggest that the PSR J1906+0746 binary system might be a younger version of the double pulsar system , intensive searches for radio pulses from the companion have so far been unsuccessful .
It is therefore not known whether the companion is another neutron star or a massive white dwarf .
Regardless of the nature of the companion , a simple calculation suggests that the Galactic birth rate of binaries similar to PSR J1906+0746 is \sim 60 Myr ^ { -1 } .
This implies that PSR J1906+0746 will make a significant contribution to the computed cosmic inspiral rate of compact binary systems .