A Search for Millisecond Pulsars at Galactic Latitudes -50 degrees < B < -20 degrees

We have detected 12 new pulsars, including four of the short-period "recycled" variety, in a survey using the Arecibo radio telescope at 430 MHz. The survey covered 680 square degrees at right ascensions 21h through 02h, declinations +7 through + 30°. Most of the region falls between Galactic latitudes -20° and -50°. The minimum detectable flux density for long-period pulsars was approximately 0.5 mJy for declinations +14° -3 pc the detection threshold was about 10 mJy. Only one previously known pulsar lay within the search region, and it was detected easily. The newly discovered short-period pulsars include two isolated objects: PSR J2322+2057 (P = 4.81 ms, DM = 13 cm-3 pc), and PSR J2235+1506 (P = 59:8 ms, DM = 18 cm-3 pc); and two pulsars in nearly circular binary orbits: PSR J2229+2643 (P = 2.98 ms, DM = 23 cm-3 pc, orbital period Pb = 93d), and PSR J2317+1439 (P = 3.45 ms, DM = 22 cm-3 pc, Pb = 2.d5) We present timing observations of three of these pulsars over 1.5-2.5 yr. Refined and extended data sets for PSRs J2235+1506 and J2317+1439 have allowed the first measurements of their proper motions, which imply velocities of (100±40) km s-1 and (70±30) km s-1, respectively. Timing measurements of PSR J2229+2643 show that it has the smallest period derivative of any known pulsar, Pdot = (1.9±0.2) x 10-21. We use this result to establish a new upper limit for the possible rate of change of the Newtonian constant of gravity, |Gdot/G| -11 yr-1.