We present long-term timing observations of four millisecond radio pulsars with the 305 m Arecibo and the 100 m Effelsberg radiotelescopes. Our analysis of the combined pulse time-of-arrival data from the two telescopes has led to improvements of the precision of timing parameter determination for all the four pulsars. A new, much more significant measurement of a third-order spin frequency derivative of PSR B1257 + 12 adds to the existing evidence that a fourth, distant planet may orbit this pulsar. Proper motions have been measured for PSR J1640 + 2224, PSR B1953 + 29, and PSR J2229 + 2643. The derived low transverse velocities of these objects agree with the kinematic characteristics of the observed millisecond pulsar population. Exceptionally low spindown rates of PSR J1640 + 2224 and PSR J2229 + 2634 have been used to derive useful limits on the initial spin periods of these objects and on the variation of the gravitational constant G.
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science