Constraints on the putative companions to PSR1257+12

The radio pulsar PSR1257+12 was first observed about two years ago at the Arecibo radio telescope. It has a pulse period of 6.2 milliseconds which makes it one of only a handful of known objects of this type that spin at a dizzying rate of several hundred times per second. Routine follow-up monitoring of this object has continued since its discovery. The pulsar's discoverer has recently reported that a standard analysis of the time-of-arrival measurements of the radio pulses from PSR1257+12 showed that after accounting for the usual features of millisecond pulsars, there remained a residual in the signal which appeared to be a superposition of two components, one with a period of 98 days and the other with a period of 66 days. This was interpreted as being due to the presence of two low mass companions in orbit about the pulsar. The amplitude of the individual components in the residuals then gives a measure of the masses of the companions, up to a factor 1/sin i where i is the inclination of the orbital plane to the plane of the sky, so that a lower limit of the companion masses is well defined. The work reported in this paper tests the validity of this interpretation through orbital dynamics.