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29 March 2024 |
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Article overview
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Asymmetries on red giant branch surfaces from CHARA/MIRC optical interferometry | A. Chiavassa
; R. Norris
; M. Montargès
; R. Ligi
; L. Fossati
; L. Bigot
; F. Baron
; P. Kervella
; J. D. Monnier
; D. Mourard
; N. Nardetto
; G. Perrin
; G. H. Schaefer
; T. A. ten Brummelaar
; Z. Magic
; R. Collet
; M. Asplund
; | Date: |
7 Mar 2017 | Abstract: | Context. Red giant branch (RGB) stars are very bright objects in galaxies and
are often used as standard candles. Interferometry is the ideal tool to
characterize the dynamics and morphology of their atmospheres. Aims. We aim at
precisely characterising the surface dynamics of a sample of RGB stars.
Methods. We obtained interferometric observations for three RGB stars with the
MIRC instrument mounted at the CHARA interfer- ometer. We looked for
asymmetries on the stellar surfaces using limb-darkening models. Results. We
measured the apparent diameters of HD197989 (Epsilon Cyg) = 4.61+-0.02 mas,
HD189276 (HR7633) = 2.95+-0.01 mas, and HD161096 (Beta Oph) = 4.43+-0.01 mas.
We detected departures from the centrosymmetric case for all three stars with
the tendency of a greater effect for lower logg of the sample. We explored the
causes of this signal and conclude that a possible explanation to the
interferometric signal is the convection-related and/or the magnetic-related
surface activity. However, it is necessary to monitor these stars with new
observations, possibly coupled with spectroscopy, in order to firmly establish
the cause. | Source: | arXiv, 1703.2406 | Services: | Forum | Review | PDF | Favorites |
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