ACCRETION ON TO STRANGE-MATTER PULSARS

We study the effects of the accretion of normal matter on to strange-m atter pulsar models. It is assumed that, because of the high strangene ss barrier, normal matter is inert in contact with Q(alpha) matter. Fo r this reason, normal matter accretion is able to form a thick outer l ayer with densities far above neutron drip. Accretion can make the sup erfluid quark-alpha Q(alpha) layer disappear by solidification but, fo r the same reason, a superfluid neutron layer is formed. The fractiona l moment of inertia of the latter is large enough to fulfil the vortex -creep glitch model requirements. The high rotational stability of mil lisecond pulsars is discussed in the framework of the strange-matter h ypothesis. If the validity of the vortex-creep model is assumed, it is shown that, for the case of accreted strange-pulsar models, this stab ility cannot be interpreted as due to the solidification of the superf luid Q(alpha) layer. Nevertheless,`standard' homogeneous strange stars remain as interesting candidates for the internal composition of thes e objects. The main conclusions of this work should be unaltered if Q( alpha) is not preferred to strange matter at low pressures, but some o ther strange complex plays a similar role.