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Paper: PIONIERing Diameter Measurements of Globular Cluster Giants
Volume: 497, Why Galaxies Care about AGB Stars III: A Closer Look in Space and Time
Page: 485
Authors: Hron, J.; Bouquin, J. L.; Lebzelter, T.; Paladini, C.; Soszynski, I.; Berger, J.-P.; Boffin, H. M. J.; Wittkowski, M.
Abstract: We present an attempt to resolve for the first time one of the brightest long period variables in the globular cluster 47 Tuc with PIONIER in the H band. Based on model atmospheres and observations of local LPVs, the predicted visibilities were about 0.9, i.e. they are at the limit of feasibility with PIONIER. The observations show that the star is unresolved with an upper limit of 0.44 mas for the uniform disk (UD) diameter in the H band. This is in agreement with the predictions from stellar evolution models and from a dynamic model with similar stellar parameters. Spatial frequencies of B[m] / λ[μm]> 150 are necessary to resolve this star and to distinguish between different models, but these are beyond those currently accessible with VLTI.
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