On the mechanism of low-mass compact object formation
  We suggest that low-mass compact objects (hadron stars, quark stars) with $M<1 M_{\odot}$ can appear only due to fragmentation of rapidly rotating proto-neutron stars. Such low-mass stars receive large kicks due to an explosion of a lighter companion in a pair of fragments, or due to dynamical ejection of one of the lighter components in the case when three bodies are formed.   As far as low-mass compact objects are expected to be slowly cooling in all popular models of thermal evolution possible candidates are expected to be found among hot high velocity sources. 
S.B. Popov