Abstract
Hot subdwarf stars (hot sds) are blue subluminous objects at high galactic latitudes. They split into two well-separated spectroscopic sequences: the O (sdOs) and B-type (sdBs), according to composition and effective temperature. As they are immediate progenitors of white dwarfs (WDs), this resembles the spectroscopic H (DA)/He (DB) distinction between these. Among the various theories for the origin and final fate of hot sds, both single and close binary evolution have been suggested but the issue is still debated. Only a few determinations are available to date regarding the study of such aspects as rotation and microturbulent velocities (Heber et al.~2000) or the magnetic nature of these objects (Elkin 1996).
