||VLTI/AMBER Studies of the Atmospheric Structure and Fundamental Parameters of Red Giant and Supergiant Stars
||497, Why Galaxies Care about AGB Stars III: A Closer Look in Space and Time
||Arroyo-Torres, B.; Wittkowski, M.; Marcaide, J. M.; Abellan, F. J.; Chiavassa, A.; Fabregat, J.; Freytag, B.; Guirado, J. C.; Hauschildt, P. H.; Marti-Vidal, I.; Quirrenbach, A.; Scholz, M.; Wood, P. R.
||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 constraining the fundamental
parameters of these objects.
The observed visibilities of six red supergiants (RSGs), and also of
one of the five red giants observed, indicate large extensions of the
molecular layers, as 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 Rosseland angular radii
for 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