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Session: Stars, Planets and the Interstellar Medium

Name: Mr. Kostas Antoniadis (National Observatory of Athens / NKUA)
Coauthors: Bonanos Alceste (National Observatory of Athens)
Yang Ming (Chinese Academy of Sciences)
de Wit Stephan (National Observatory of Athens / NKUA)
Zapartas Emmanouil (National Observatory of Athens)
Munoz-Sanchez Gonzalo (National Observatory of Athens / NKUA)
Maravelias Grigoris (National Observatory of Athens)
Tramper Frank (KU Leuven)
Christodoulou Evangelia (National Observatory of Athens / NKUA)
Type: Poster
Title: The mass-loss rates of Red Supergiants in the Large Magellanic Cloud
Abstract:

The mass loss in the case of massive stars can affect many areas of astrophysics, such as the ionising radiation, the wind feedback, stellar remnants, and supernovae. The mass-loss mechanism of Red Supergiants (RSGs), which are cool massive stars with strong winds, is still poorly understood. Atmospheric turbulence, pulsations that lift the gas to a few stellar radii and radiation pressure on the newly formed dust in the circumstellar environment contribute to this mechanism. Evolutionary models have shown that high mass-loss rates can affect the fate of RSGs. Various empirical prescriptions scaled with luminosity have been derived in literature providing different results with significant dispersion. We studied the largest sample of RSG candidates (~5000 in the Large Magellanic Cloud), till now, to provide a better understanding of the mass-loss rate relation with luminosity, and hence the underlying physical mechanism. The dust formed in the circumstellar environment appears as infrared excess in the spectrum, making the availability of mid-infrared photometry significant to derive the properties of the dust shell. We used photometry in around 40 bands, ranging from ultraviolet to mid-infrared, and we fitted the Spectral Energy Distributions (SEDs) with models generated by the radiative transfer code DUSTY. We expanded this work to lower metallicity environments, 250 RSGs in NGC 6822, for which we discuss our first results. After deriving the luminosities from the SEDs and estimating stellar and circumstellar dust parameters from the best-fit models, such as the effective temperature, dust temperature, and optical depth, we derived the mass-loss rates. We found a power-law relation of the mass-loss rate with luminosity for targets with logL>4 Lo. A roughly constant mass-loss rate is found for lower luminosity targets. Finally, we compare our results with the empirical prescriptions in the literature.