LIMITS ON PLANETS ORBITING MASSIVE STARS FROM RADIO PULSAR TIMING

When a massive star collapses to a neutron star, rapidly losing over o ne-half its mass in a symmetric supernova explosion, any planets orbit ing the star will be unbound. However, to explain the observed space v elocity and binary fraction of radio pulsars, an asymmetric kick must be given to the neutron star at birth. Occasionally, this kick will pr event the resulting pulsar-planet system from unbinding. We estimate t he survival probability of a Jupiter-type planet in an asymmetric supe rnova explosion and show that if a typical massive star has one such p lanet, then several known nonmillisecond pulsars should possess planet ary companions in highly eccentric orbits. Conversely, if pulsar timin g measurements fail to detect planets orbiting these pulsars, then the average number of such planets per star is less than about 0.5.