Abstract

We have discovered 21 pulsars, including two with short pulse periods in binary systems, in a continuing survey using the Arecibo radio telescope at 430 MHz. The survey region consists of a set of eight disjoint strips of constant declination, each 1° wide. To date, we have observed 53% of the sky in these strips, or a total of 1428 deg². Our sample interval was 250 μs, so pulsars at low dispersion measures with periods as short as 500 μs could have been detected if strong enough. At high Galactic latitudes, our limiting sensitivity was in the range 0.4-1.1 mJy for pulsars with periods longer than 60 ms. Higher flux-density limits apply for shorter periods and high dispersion measures. In addition to the newly discovered pulsars, we "rediscovered" 19 previously known pulsars, including all of those expected to be detectable.

We have timed the two new binary pulsars with the Arecibo 305 m telescope, the Green Bank 140 foot (43 m) telescope, and the Jodrell Bank 76 m telescope. PSR J0621 +1002 is a 28.9 ms pulsar in an 8.3 day orbit with eccentricity 0.0025, and PSR J1022 +1001 is a 16.5 ms pulsar in a 7.8 day orbit with eccentricity 10^-4. The orbital parameters imply minimum companion masses of 0.45 and 0.73 M_sun, respectively, significantly more massive than most white dwarf companions of millisecond pulsars. These two pulsar systems, along with those of PSRs J2145-0750 and B0655+64, form a class of intermediate-mass pulsar binaries whose characteristics include spin periods above 10 ms and eccentricities somewhat higher than their low-mass counterparts.