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Session: Stars, Planets and the Interstellar Medium

Name: Dr. Alceste Bonanos (National Observatory of Athens)
Coauthors: Maravelias Grigoris (NOA, IA-FORTH)
Yang Ming (National Astronomical Observatories, Chinese Academy of Sciences, China)
Tramper Frank (KU Leuven, Belgium)
de Wit Stephan (NOA, NKUA)
Zapartas Emmanouil (NOA)
Antoniadis Konstantinos (NOA, NKUA)
Christodoulou Evangelia (NOA, NKUA)
Munoz-Sanchez Gonzalo (NOA, NKUA)
Type: Oral
Title: Results of the ASSESS project: Episodic Mass Loss in Evolved Massive Stars: Key to Understanding the Explosive Early Universe
Abstract:

Episodic mass loss is not understood theoretically, neither accounted for in state-of-the-art models of stellar evolution, which has far-reaching consequences for many areas of astronomy. We present the status and results of the ERC-funded ASSESS project (2018-2024), which aims to determine whether episodic mass loss is a dominant process in the evolution of the most massive stars, by conducting the first extensive, multi-wavelength survey of evolved massive stars in the nearby Universe. It hinges on the fact that mass-losing stars form dust and are bright in the mid-infrared. We aim to derive physical parameters of ~1000 dusty, evolved massive stars in ~25 nearby galaxies and estimate the amount of ejected mass, which will constrain evolutionary models, and quantify the duration and frequency of episodic mass loss as a function of metallicity. The approach involves selecting dusty, luminous targets from existing multi-band photometry of nearby galaxies. We present an overview of the spectroscopic survey, the machine-learning classifier for evolved massive stars, the modeling that is underway and the mass-loss rate of red supergiants determined in the Small Magellanic Cloud. The emerging trend for the ubiquity of episodic mass loss, if confirmed, will be key to understanding the explosive early Universe and will have profound consequences for low-metallicity stars, reionization, and the chemical evolution of galaxies.