The impact of binary stars in the determination of the total mass of stellar system.

Binary stars play a very important role in the dynamics of stellar systems such as star clusters. After a detailed analysis of binary classification, formation mechanisms and both fundamental parameters and distributions, the impact of binaries in the determination of the total cluster mass has been investigated by means of N-body simulations founded on the code NBODY7. Since the primordial binary fraction is a crucial ingredient in star cluster dynamical evolution, three open-clusters-like models characterised by a different initial binary percentage have been realised and a careful examination of their outputs has been performed. In the end, two HRD-based methods, i.e. the photometric and the isochrone fitting methods, have been employed to point out the fact that either neglecting the presence of binaries or not accounting for them properly leads to definitely wrong mass estimates.