Linking bIrth and death: an Empirical approach To lumInous blue Massive star Evolution


Recent investigations have dented confidence in state-of-the-art models of massive star evolution. As a result, our current understanding of how massive stars evolve has become a disorganized puzzle with many missing pieces. LIfETIME will reconstruct this broken puzzle following a novel strategy, based on a purely empirical interpretation of a densely populated multidimensional Hertzsprung-Russell (HR) diagram covering the full OB star domain. Under this fully empirical approach, we plan to provide concrete answers to two big scientific questions:

- What is the combined impact that mass, stellar winds, rotation, and binarity have on the evolution of massive stars?
- What other physical mechanisms are relevant for the evolution of massive stars from the Main Sequence to the SNe explosion?
LIfETIME will be developed in coordination with the project "ONStaGE: An Observational laNdscape for SupernovA and Gravitational wavE progenitors", led by I. Negueruela and A. Marco (Universidad de Alicante). Both subprojects together constitute the coordinated project "MEASuRE: A Massive Empirical Approach to Stellar Evolution: from protostars to core collapse supernovae and gravitational wave progenitors"

To drive scientific advance, LIfETIME will benefit from observations gathered by several modern spectroscopic surveys of Galactic massive stars and the revolutionary distance data provided by Gaia (complemented with extragalactic spectra) . In addition, team members of this AYA project in coordination with our colleagues from the massive star team in Alicante will develop and exploit innovative automated tools for the quantitative spectroscopic analysis of large samples of OB stars, and advanced tools for data handling, visualization and machine learning. LIfETIME will also prepare for future research in hidden Galactic regions by extending its observations and tools to the NIR.
LIfETIME will be guided by the following intermediate questions:

- How many different groups of OB stars with homogeneous properties can be found at different evolutionary stages?
- What are the best empirical quantities (or relation between quantities) to identify whether a given target in the HR diagram has followed a single star evolutionary track or is the product of binary interaction?
- What is the percentage of massive OB stars showing clear signatures of binary evolution at different evolutionary stages and mass ranges?
- What's the role of extreme peculiar phases like hot hypergiants and LBVs?
- What is the best recipe to describe angular momentum and mass loss evolution (as well as the interplay between both)?
- What other mechanisms, in addition to rotation, can drive mixing of chemical species from the interior of the star to the stellar surface?

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This project aims at the searching, observation and analysis of massive stars in nearby galaxies to provide a solid empirical ground to understand their physical properties as a function of those key parameters that gobern their evolution (i.e. mass, spin, metallicity, mass loss, and binary interaction). Massive stars are central objects to
Simón Díaz