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On the atmospheric structure and fundamental parameters of red supergiants

Published online by Cambridge University Press:  23 January 2015

M. Wittkowski ,
B. Arroyo-Torres ,
J. M. Marcaide ,
F. J. Abellan ,
A. Chiavassa ,
B. Freytag ,
M. Scholz ,
P. R. Wood  and
P. H. Hauschildt
M. Wittkowski
Affiliation:
ESO Garching, Germany, email: mwittkow@eso.org
B. Arroyo-Torres
Affiliation:
University of València, Spain
J. M. Marcaide
Affiliation:
University of València, Spain DIPC, Donostia-San Sebastian, Spain
F. J. Abellan
Affiliation:
University of València, Spain
A. Chiavassa
Affiliation:
University of Nice Sophia-Antipolis, France
B. Freytag
Affiliation:
Uppsala University, Sweden
M. Scholz
Affiliation:
University of Heidelberg, Germany and University of Sydney, Australia
P. R. Wood
Affiliation:
Australian National University, Canberra, Australia
P. H. Hauschildt
Affiliation:
Hamburg Observatory, Germany
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Abstract

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We present near-infrared spectro-interferometric studies of red supergiant (RSG) stars using the VLTI/AMBER instrument, which are compared to previously obtained similar observations of AGB stars. Our observations indicate spatially extended atmospheric molecular layers of water vapor and CO, similar as previously observed for Mira stars. Data of VY~CMa indicate that the molecular layers are asymmetric, possibly clumpy. Thanks to the spectro-interferometric capabilities of the VLTI/AMBER instrument, we can isolate continuum bandpasses, estimate fundamental parameters of our sources, locate them in the HR diagram, and compare their positions to recent evolutionary tracks. For the example of VY CMa, this puts it close to evolutionary tracks of initial mass 25-32 M⊙. Comparisons of our data to hydrostatic model atmospheres, 3d simulations of convection, and 1d dynamic model atmospheres based on self-excited pulsation models indicate that none of these models can presently explain the observed atmospheric extensions for RSGs. The mechanism that levitates the atmospheres of red supergiant is thus a currently unsolved problem.

Keywords

convectiontechniques: interferometricstars: atmospheresstars: evolutionstars: fundamental parametersstars: individual (VY CMa, KW Sgr, UY Sct, AH Sco, V602 Car, HD 95687)stars: mass losssupergiants
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 9 , Issue S307: New windows on massive stars: asteroseismology, interferometry, and spectropolarimetry , June 2014 , pp. 280 - 285
Copyright
Copyright © International Astronomical Union 2015 

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