Formation of massive skyrmion stars

We discuss different channels of formation of massive rapidly rotating neutron stars. We use a population synthesis code to estimate numbers of massive neutron stars in different evolutionary stages. For stiff equations of state the existence of neutron stars with masses greater than or similar to 2 M. is possible. An especially interesting situation occurs if the equation of state based on the Skyrme theory is realized in nature. A neutron star increases its mass by accretion from a secondary companion. Significant growth of a neutron star mass due to accretion is possible only for certain values of initial parameters of the binary. In this paper we show that a significant part of massive neutron stars with M greater than or similar to 2 M. can be observed as millisecond radio pulsars, as X- ray sources in pairs with white dwarfs, and as accreting neutron stars with very low magnetic fields.