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New Determinations of the Proper Motions of 44 Pulsars PA Mon. Not. R. Astron. Soc. 261,113-124 (1993) .113H New determinations of the proper motions of 44 pulsars 93MNRAS.261. 19 P. A. Harrison, A. G. Lyne and B. Anderson University of Manchester, Nuffield Radio Astronomy Laboratories, Jodrell Bank, Macclesfield, Cheshire SKI 1 9DL Accepted 1992 August 28. Received 1992 August 28; in original form 1992 May 22 ABSTRACT A programme of observations to measure the proper motions of 44 pulsars has been carried out at Jodrell Bank over a four-year period, yielding 31 determinations of proper motion and 13 upper limits. Observations were carried out with two interfero- meters of the MERLIN radio synthesis instrument at 408 MHz. By wide-field phase referencing to multiple sources within the primary beam of the instrument, accurate positions of each pulsar relative to its reference sources have been determined for a number of epochs. The change in the measured position with epoch results in the determination of the proper motion of the pulsar, using a method similar to that of Lyne, Anderson & Salter. The new measurements double the number of interfero- metrically measured proper motions and reinforce the general picture which emerged from that study, i.e. pulsars form a population of high-velocity objects (with rms speed - 300 km s~1 ) which seem to be migrating from the galactic plane. The new kinetic age determinations also support the conclusion that the magnetic fields of pulsars decay on time-scales of a few million years. The observation of a small number of pulsars moving towards the galactic plane, however, implies that there is a small population of pulsars born far from the plane, requiring some modification of the traditionally held views about pulsar birthplaces. Key words: astrometry - pulsars: general. 1 INTRODUCTION the largest is that of Lyne et al, (1982) (hereafter LAS), who made proper motion measurements of 26 pulsars. The Measurements of the proper motions of pulsars indicate that current survey of 44 pulsars is intended to be an extension of they have large space velocities and their study can be used that study, but includes three pulsars in common in an to investigate a wide variety of phenomena, from the forma- attempt to improve upon Lyne et al.’s measurements. tion of neutron stars to the details of their ageing. The proper motion itself can be used to trace a pulsar back to its birth- place and hence to check its association with a supernova 2 THE OBSERVATIONS remnant, as has been done recently for the Vela pulsar 2.1 The observing technique (Bailes et al. 1989). It can also be used to derive an indepen- dent measure of a pulsar’s age which can then be used to The measurements were carried out using a technique study the evolution of neutron star magnetic fields. similar to that described by LAS. Observations were made at It is possible to measure the proper motions of pulsars 408 MHz using wide-field phase referencing to sources through pulse timing analysis (Manchester, Taylor & Van within the primary beam of the interferometer (Peckham 1974; Helfand, Taylor & Manchester 1977; Downs & 1973). Astrometry could then be performed to determine Reichley 1983; Rawley, Taylor & Davis 1988), or through the relative position of the pulsar with respect to its reference traditional optical methods (Wyckoff & Murray 1977; sources, enabling much higher accuracy than would be Bignami & Caraveo 1988). However, the most productive possible with absolute astrometry. method so far has been the use of radio interferometry, There were, however, a number of significant improve- whether it be by linked interferometer (Anderson, Lyne & ments on the LAS experiment. First, two baselines from the Peckham 1975; Lyne, Anderson & Salter 1982; Backer & MERLIN system were used rather than one: the 76-m Lovell Sramek 1982; Bailes et al. 1990; Fomalont et al. 1992), or telescope at Jodrell Bank with the 26-m antenna at Defford VLBI (Gwinn et al. 1986), since proper motions from timing and with the 25-m antenna at Knockin, providing baselines observations are difficult to measure except for pulsars with of 127 and 68 km respectively. The second, shorter, baseline low timing noise. Of the radio interferometric studies, by far allowed the use of reference sources which were fully © Royal Astronomical Society • Provided by the NASA Astrophysics Data System 114 P. A. Harrison, A. G. Lyne and B. Anderson .113H Table 1. Positions and proper motions of 44 pulsars. The assumed positions of the pulsars are given, together with the number of reference sources, Nrd, and the proper motions in right ascension and declination. Note that jua = (da/dt) cos <5. is the normalized covariance of the two components of the proper motion. The total proper motion and its position angle are given, together with the proper motion in galactic coordinates, corrected for differential galactic rotation and solar motion (see Section 3). 93MNRAS.261. Pulsar a (J2000) ó (J2000) Nrcf Ma t¿6 PpaHi Mtota.1 Mi Mb 19 mas yr“1 mas yr“1 masyr“ mas yr“1 mas yr“1 0136+57 013919.876 5814 31.99 5 -11+5 -19+5 0.25 22+5 -150+13 -6+5 -20+5 0148-06 01 51 22.628 -06 35 00.30 4 15+47 -30+34 0.55 34+58 26+52 -17+26 0320+39 03 23 26.604 39 44 53.92 4 16+6 -30+5 0.06 34+5 152+10 28+6 -14+5 0329+54 03 32 59.314 54 34 42.73 1 17+1 -13+1 0.47 21 + 1 127+3 22+1 0+1 0447-12 04 50 08.759 -12 48 06.76 6 0+20 -3+18 0.06 3+27 3+19 -2+19 0450+55 04 54 07.600 55 43 39.50 2 52+6 -17+2 -0.01 55+6 108+3 40+4 34+5 0458+46 05 02 04.500 46 54 04.95 1 -8+3 8+5 0.26 11+4 -45+21 -13+5 0+3 0523+11 05 25 56.374 11 15 15.40 3 30+7 -4+5 0.24 30+7 98+9 19+6 24+6 0525+21 05 28 52.192 22 00 22.80 3 -20+19 7+9 0.62 21 + 18 -71+29 -18+16 -12+13 0540+23 05 43 09.600 23 29 06.19 2 19+7 12+8 0.08 22+7 58+20 -1+8 23+7 0559-05 06 01 58.974 -05 27 49.66 2 18+8 -16+7 0.48 24+8 132+18 23+9 9+6 0611+22 06 1417.220 22 29 58.80 3 -4+5 -3+7 0.24 5+9 0+7 -4+5 0626+24 06 29 05.664 2415 56.78 3 -7+12 2+12 0.34 7+17 -5+14 -5+10 0643+80 06 53 14.679 80 51 59.61 2 19+3 -1+3 -0.10 19+3 93+9 2+3 19+3 0655+64 07 00 37.805 6418 11.29 4 1+35 -14+29 -0.19 14+45 5+28 3+36 0751+32 07 54 40.627 32 31 57.44 5 -4+5 7+3 -0.16 8+4 -30+33 -9+3 0+5 0818-13 08 20 26.314 -13 50 54.86 2 9+10 -31+7 0.43 32+7 164+17 34+10 -7+8 0820+02 08 23 09.750 0159 12.69 4 5+11 -1+8 0.09 5+14 5+9 8+10 0906-17 09 08 38.124 -17 39 36.55 3 27+11 -40+11 0.48 48+11 146+13 54+13 1+8 0919+06 09 22 13.894 06 38 21.65 5 13+29 64+37 0.12 65+37 11+26 -48+37 46+29 0940+16 09 43 31.046 16 31 21.88 2 23+16 9+11 0.23 25+15 69+27 1+13 30+14 0942-13 09 44 28.923 -1354 41.44 5 -1+32 -22+14 0.10 22+14 -177+83 22+25 -9+25 1112+50 11 15 38.333 50 30 13.88 4 22+3 -51+3 -0.25 56+3 157+3 14+3 54+3 1322+83 13 2145.787 83 23 37.98 2 -53+20 13+7 -0.36 55+19 -76+9 52+19 -5+8 1718-02 17 20 57.243 -0212 23.19 2 26+9 -13+6 -0.15 29+8 117+13 3+7 -28+8 1821+05 18 23 31.014 05 50 24.75 3 5+11 -2+4 0.14 5+12 3+6 -4+10 1839+56 18 40 44.390 56 40 53.96 1 -30+4 -21+2 -0.14 37+3 -125+4 -24+2 25+4 1842+14 18 44 54.885 14 5413.89 1 -9+10 45+6 -0.22 46+6 -11 + 12 40+8 29+9 1905+39 19 07 34.808 40 02 06.04 2 11+4 11 + 1 -0.33 16+3 45+11 19+2 -5+4 1911-04 19 13 54.204 -0440 47.59 2 7+13 -5+9 0.41 9+16 1+8 -8+14 1917+00 19 19 50.661 00 2140.19 4 -2+30 -1 + 10 0.03 2+32 2+16 2+27 1937+21 19 39 38.585 21 34 59.26 3 -2+4 -3+3 -0.20 4+3 -146+59 2+4 1+3 1946+35 19 48 25.068 35 4011.23 3 -9+7 -4+8 0.03 10+8 -110+50 -3+8 6+7 1953+50 19 55 18.934 50 59 54.15 4 -23+5 54+5 -0.79 59+5 -23+5 40+6 47+3 2043-04 20 46 00.138 -04 21 25.24 3 9+16 -7+8 0.46 11 + 18 1+8 -10+16 2044+15 20 46 39.404 15 40 32.53 3 -13+6 3+4 0.27 13+6 -77+18 -1+4 13+6 2053+36 20 55 31.369 36 30 21.03 3 -3+7 3+3 -0.10 4+8 5+5 5+6 2110+27 21 13 04.433 27 54 02.64 4 -23+2 -54+3 -0.03 59+3 -157+2 -52+3 -16+2 2113+14 21 16 13.774 1414 21.22 2 8+15 -11+5 0.12 14+10 144+53 1+10 -13+13 2148+63 2149 58.632 63 29 43.31 3 14+3 10+4 -0.28 17+3 54+12 21+4 -1+3 2154+40 21 57 01.942 4017 44.92 2 18+1 -3+1 0.11 18+1 99+3 17+1 -13+1 2224+65 22 25 52.270 65 35 31.64 2 144+3 112+3 0.10 182+3 52.1+0,9 184+3 19+3 2306+55 23 08 13.928 55 47 35.13 2 -15+8 0+27 -0.41 15+8 -90+100 -11+15 7+24 2351+61 23 54 04.681 6155 47.94 2 22+3 6+2 ^-0.10 23+3 75+5 25+3 2+2 resolved on the longer baseline, as well as giving an inde- reference sources (given in Table 1) for each pulsar being pendent measure of position.
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