Interplay between evolved massive stars and their circumstellar mediuma (SUB) millimetre view of luminous blue variable mass loss

Résumé

Massive stars play a significant role in the shaping and evolution of the Galaxy. Their stellar winds and strong UV fields continuously alter the structure, dynamics and chemical composition of the surrounding ISM. Still, their impact becomes even more relevant once they leave the main sequence. They turn unstable and progressively lose a significant fraction of their initial mass, evolving through a series of transitional phases toward their inevitable end as core-collapse supernovae. Among these post-main sequence stages, the luminous blue variable (hereafter LBV) phase acquires a particular relevance. Short-lived ( 104 yr) and intrinsically variable, the LBV phase exhibits the highest mass-loss rates –with values up to 10 4or 10 3 M y r 1–, by virtue of dense and steady winds often accompanied by violent outbursts that expel the outer stellar layers into the ISM. These processes lead to the formation of large and heterogeneous circumstellar nebulae of dust and gas, in which the mass-loss record of the central star is written. Despite having been exhaustively studied for decades at optical, infrared, and radio continuum wave lengths, the LBVphase still poses some of the most challenging questions of stellar astrophysics: whichis the evolutionary role of these objects? what drives their instability? which factors determine the shaping of the nebulae?...