The Orbital Evolution and Proper Motion of PSR J2051−0827

Abstract

We have carried out high-precision timing observations of the eclipsing binary PSR J2051-0827 in the 3.3 years since its discovery. The data indicate that the orbital period is decreasing at a rate of P dot b = (-11 +/- 1) x 10-12. If secular, this orbital period derivative implies a decay time for the orbit of only 25 Myr, which is much shorter than the expected timescale for the ablation of the companion. We have also measured the proper motion of the pulsar to be 5+/-3 mas yr ^{-1} . Assuming the pulsar is at the dispersion-measure distance, this implies a very slow transverse velocity vt=(30+/-20) km s ^{-1} . This combination of low velocity and short orbital period argues against the formation of the system in the standard manner, and we discuss the implications for its evolutionary history.