We present the discovery of a binary millisecond pulsar ( MSP ) , PSR J2322 - 2650 , found in the Southern section of the High Time Resolution Universe survey .
This system contains a 3.5-ms pulsar with a \sim 10 ^ { -3 } M _ { \odot } companion in a 7.75-hour circular orbit .
Follow-up observations at the Parkes and Lovell telescopes have led to precise measurements of the astrometric and spin parameters , including the period derivative , timing parallax , and proper motion .
PSR J2322 - 2650 has a parallax of 4.4 \pm 1.2 mas , and is thus at an inferred distance of 230 ^ { +90 } _ { -50 } pc , making this system a candidate for optical studies .
We have detected a source of R \approx 26.4 mag at the radio position in a single R -band observation with the Keck Telescope , and this is consistent with the blackbody temperature we would expect from the companion if it fills its Roche lobe .
The intrinsic period derivative of PSR J2322 - 2650 is among the lowest known , 4.4 ( 4 ) \times 10 ^ { -22 } s s ^ { -1 } , implying a low surface magnetic field strength , 4.0 ( 4 ) \times 10 ^ { 7 } G. Its mean radio flux density of 160 \mu Jy combined with the distance implies that its radio luminosity is the lowest ever measured , 0.008 ( 5 ) mJy kpc ^ { 2 } .
The inferred population of these systems in the Galaxy may be very significant , suggesting that this is a common MSP evolutionary path .