Investigating the evolutionary status of OB supergiants with ground-based spectroscopy, Gaia, TESS and (BRITE?)

Several decades have passed since the first empirical evidences of an overdensity of Blue Supergiants (BSGs) in the Hertzsprung-Russell (HR) diagrams were found. This overdensity was not predicted by the evolutionary models that instead expected a gap (the "Hertzsprung gap"), and therefore forced us to come with more complex interior models and new physical explanations to try to reproduce the observables. As new questions emerge from trying to solve the nature of these stars, the complexity of the problem does just only increase. The relevance of using as much homogeneous and non-biased empirical data is now more crucial than ever. By using high-resolution spectroscopy of one of the largest samples of BSGs gathered from the IACOB database, we have first found a strong match between the drop in density of stars in the HR diagram and their rotation speed that points to a new end of the Main Sequence (MS) in the range of 9-85 solar masses. In the upcoming future, we will add empirical information from abundances, wind parameters, variability (from TESS, and probably BRITE) and environmental information (Gaia) to serve as a strong constraints for the upcoming evolutionary models. They will have to explain not only these new MS stars but also their evolved descendants, which could belong to two different populations depending if they are moving towards or back from the Red Supergiant phase.