Magnetars origin and progenitors with enhanced rotation

Among a dozen known magnetar-candidates there are no binary objects. As an estimate of a fraction of binary neutron stars is about 3-10% it is reasonable to address the question of solitarity of magnetars, to estimate theoretically the fraction of binary objects among them, and to mark out the most probable companions. We present population synthesis calculations of binary systems. In this study we assume the hypothesis that magnetic field of a magnetar is generated at the protoneutron star stage due to dynamo mechanism, so rapid rotation of the core of a progenitor star is essential. Our goal is to estimate the number of neutron stars originated from progenitors with enhanced rotation. In our calculations the fraction of neutron stars originated from such progenitors is about 8-9%. This should be considered as an upper limit to the fraction of magnetars as some of progenitors can loose momentum. Most of these objects are isolated due to coalescences of components prior to a neutron star formation, or due to a system disruption after the second supernova explosion. The fraction of such neutron stars in survived binaries is about 1% or lower. Their most numerous companions are black holes.