VLTI/AMBER studies of the atmospheric structure and fundamental parameters of red giant and supergiant stars

• We present recent near-IR interferometric studies of red giant and supergiant stars, which are aimed at obtaining information on the structure of the atmospheric layers and at constraining the fundamental parameters of these objects. The observed visibilities of the red supergiants (RSGs) and also of one red giant indicate large extensions of the molecular layers, as those previously observed for Mira stars. These extensions are not predicted by hydrostatic PHOENIX model atmospheres, hydrodynamical (RHD) simulations of stellar convection, or self-excited pulsation models. All these models based on parameters of RSGs lead to atmospheric structures that are too compact compared to our observations. We discuss how alternative processes might explain the atmospheric extensions for these objects. As the continuum appears to be largely free of contamination by molecular layers, we can estimate reliable angular Rosseland radii of our stars. Together with distances and bolometric fluxes, we estimate the effective temperatures and luminosities of our targets, locate them in the HR diagram, and compare their positions to recent evolutionary tracks.

Ämnesord

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Nyckelord

MOLECULAR LAYERS

AMBER/VLTI

OPACITY-SAMPLING MODELS

DATA REDUCTION

VY-CANIS MAJORIS

SPECTRO-INTERFEROMETRY

SIMULATIONS

EFFECTIVE TEMPERATURE

STELLAR MODELS

MIRA VARIABLES

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