Low-mass X-ray binaries are ideal sites to investigate the properties of compact objects, either neutron stars or black holes, and their connection to supernovae. The study of companion stars orbiting compact objects could provide valuable information on the origin of compact objects and their progenitors.
The secondary star could have captured some of the matter ejected from the primary star in different phases of its faster evolution, namely common envelope phase and supernova explosion. Therefore, we try to search for signatures of chemical anomalies that could have been imprinted on secondary stars during the evolution of X-ray binaries, with the aim of obtaining information on the progenitor of these compact objects. The medium/high-resolution spectroscopy that we have been obtaining in the last decade also allows us to investigate the orbital period evolution in these X-ray binary systems. I will give a brief summary of what we have done so far and our latest results on this field.
While in Type II, Ib, Ic SNe we have the advantage that the explosion leaves a compact star to which surviving companions (if they exist) often remain bound, thus enabling a large number of studies, in SNe Ia the explosion almost certainly does not produce any compact object. However, the possible companion star (if it exists) would probably have peculiar properties, like a relatively large proper-motion, over-luminosity, and may also show anomalous abundances. Our group have been investigating some Galactic historical SNIa, trying to search for the companion stars of the progenitor of historical Galactic type-Ia supernova with the aim of clarifying the origin of these cosmological candles. I will also show our latest results on this topic.