Scintillation velocities of five millisecond pulsars

Abstract

Millisecond pulsars differ from normal pulsars in their mode of origin and their properties. They are thought to be born either through binary interaction or through accretion-induced collapse (AIC) of white dwarf stars. Several theoretical considerations suggest that these different mechanisms for the origin of millisecond pulsars would lead to different distributions of the space velocities of millisecond pulsars. Therefore, it is important to estimate the average space velocity of millisecond pulsars and compare it with that of normal pulsars. Here we present transverse velocity estimates of five millisecond pulsars obtained from interstellar scintillation observations, carried out with the Ooty Radio Telescope (ORT) at 327 MHz. For the pulsars J0437-4715, B1257+12, B1534+12, J1730-2304, and J2145-0750 we obtain velocity estimates of 231, 225, 191, 56, and 113 km s^-1, respectively. The average velocity for these is much smaller than that of the normal pulsars and larger than that expected from the AIC process. Present velocity estimates are closer to other recent measurements of millisecond pulsars.