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

Abstract

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 21<SUP>h</SUP> through 02<SUP>h</SUP>, 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° &lt; σ &lt; + 23°, rising to 0.7 mJy at the declination extremes. For periods P &lt; 100 ms the minimum detectable flux density increased with decreasing period, especially for large dispersion measures; at P = 1.5 ms and DM = 10 cm<SUP>-3</SUP> pc the detection threshold was about 10 mJy. Only one previously known pulsar lay within the search region, and it was detected easily. <P />The newly discovered short-period pulsars include two isolated objects: PSR J2322+2057 (P = 4.81 ms, DM = 13 cm<SUP>-3</SUP> pc), and PSR J2235+1506 (P = 59:8 ms, DM = 18 cm<SUP>-3</SUP> pc); and two pulsars in nearly circular binary orbits: PSR J2229+2643 (P = 2.98 ms, DM = 23 cm<SUP>-3</SUP> pc, orbital period P<SUB>b</SUB> = 93d), and PSR J2317+1439 (P = 3.45 ms, DM = 22 cm<SUP>-3</SUP> pc, P<SUB>b</SUB> = 2.<SUP>d</SUP>5) 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<SUP>-1</SUP> and (70±30) km s<SUP>-1</SUP>, 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<SUP>-21</SUP>. We use this result to establish a new upper limit for the possible rate of change of the Newtonian constant of gravity, |Gdot/G| &lt; 3 x 10<SUP>-11</SUP> yr<SUP>-1</SUP>.