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Optical interferome...
Optical interferometry and Gaia measurement uncertainties reveal the physics of asymptotic giant branch stars
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- Chiavassa, A. (author)
- Univ Cote Azur, Observ Cote Azur, CNRS, CS 34229, Nice, France.
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- Kravchenko, K. (author)
- European Southern Observ, Alonso de Cordova 3107, Santiago, Chile.
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- Millour, F. (author)
- Univ Cote Azur, Observ Cote Azur, CNRS, CS 34229, Nice, France.
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- Schaefer, G. (author)
- Mt Wilson Observ, CHARA Array, Mt Wilson, CA 91023 USA.
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- Schultheis, M. (author)
- Univ Cote Azur, Observ Cote Azur, CNRS, CS 34229, Nice, France.
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- Freytag, Bernd, Dr. (author)
- Uppsala universitet,Teoretisk astrofysik
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- Creevey, O. (author)
- Univ Cote Azur, Observ Cote Azur, CNRS, CS 34229, Nice, France.
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- Hocde, V. (author)
- Univ Cote Azur, Observ Cote Azur, CNRS, CS 34229, Nice, France.
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- Morand, F. (author)
- Univ Cote Azur, Observ Cote Azur, CNRS, CS 34229, Nice, France.
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- Ligi, R. (author)
- INAF Osservatorio Astron Brera, Via E Bianchi 46, I-23807 Merate, Italy.
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- Kraus, S. (author)
- Univ Exeter, Sch Phys & Astron, Stocker Rd, Exeter EX4 4QL, Devon, England.
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- Monnier, J. D. (author)
- Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA.
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- Mourard, D. (author)
- Univ Cote Azur, Observ Cote Azur, CNRS, CS 34229, Nice, France.
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- Nardetto, N. (author)
- Univ Cote Azur, Observ Cote Azur, CNRS, CS 34229, Nice, France.
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- Anugu, N. (author)
- Univ Exeter, Sch Phys & Astron, Stocker Rd, Exeter EX4 4QL, Devon, England.;Univ Arizona, Steward Observ, 933 N Cherry Ave, Tucson, AZ 85721 USA.
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Le Bouquin, J. -B (author)
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- Davies, C. L. (author)
- Univ Exeter, Sch Phys & Astron, Stocker Rd, Exeter EX4 4QL, Devon, England.
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- Ennis, J. (author)
- Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA.
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- Gardner, T. (author)
- Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA.
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- Labdon, A. (author)
- Univ Exeter, Sch Phys & Astron, Stocker Rd, Exeter EX4 4QL, Devon, England.
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- Lanthermann, C. (author)
- Katholieke Univ Leuven, Inst Sterrenkunde, Celestijnenlaan 200D, B-3001 Leuven, Belgium.
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- Setterholm, B. R. (author)
- Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA.
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- ten Brummelaar, T. (author)
- Mt Wilson Observ, CHARA Array, Mt Wilson, CA 91023 USA.
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Univ Cote Azur, Observ Cote Azur, CNRS, CS 34229, Nice, France European Southern Observ, Alonso de Cordova 3107, Santiago, Chile. (creator_code:org_t)
- 2020-08-05
- 2020
- English.
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In: Astronomy and Astrophysics. - : EDP SCIENCES S A. - 0004-6361 .- 1432-0746. ; 640
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Abstract
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- Context. Asymptotic giant branch (AGB) stars are cool luminous evolved stars that are well observable across the Galaxy and populating Gaia data. They have complex stellar surface dynamics, which amplifies the uncertainties on stellar parameters and distances.Aims. On the AGB star CL Lac, it has been shown that the convection-related variability accounts for a substantial part of the Gaia DR2 parallax error. We observed this star with the MIRC-X beam combiner installed at the CHARA interferometer to detect the presence of stellar surface inhomogeneities.Methods. We performed the reconstruction of aperture synthesis images from the interferometric observations at different wavelengths. Then, we used 3D radiative hydrodynamics (RHD) simulations of stellar convection with CO5BOLD and the post-processing radiative transfer code OPTIM3D to compute intensity maps in the spectral channels of MIRC-X observations. Then, we determined the stellar radius using the average 3D intensity profile and, finally, compared the 3D synthetic maps to the reconstructed ones focusing on matching the intensity contrast, the morphology of stellar surface structures, and the photocentre position at two different spectral channels, 1.52 and 1.70 mu m, simultaneously.Results. We measured the apparent diameter of CL Lac at two wavelengths (3.299 0.005 mas and 3.053 +/- 0.006 mas at 1.52 and 1.70 mu m, respectively) and recovered the radius (R = 307 +/- 41 and R = 284 +/- 38 R-circle dot) using a Gaia parallax. In addition to this, the reconstructed images are characterised by the presence of a brighter area that largely affects the position of the photocentre. The comparison with 3D simulation shows good agreement with the observations both in terms of contrast and surface structure morphology, meaning that our model is adequate for explaining the observed inhomogenities.Conclusions. This work confirms the presence of convection-related surface structures on an AGB star of Gaia DR2. Our result will help us to take a step forward in exploiting Gaia measurement uncertainties to extract the fundamental properties of AGB stars using appropriate RHD simulations.
Subject headings
- NATURVETENSKAP -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)
- NATURAL SCIENCES -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)
Keyword
- stars: atmospheres
- stars: AGB and post-AGB
- stars: individual: CL Lac
- techniques: interferometric
Publication and Content Type
- ref (subject category)
- art (subject category)
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- By the author/editor
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Chiavassa, A.
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Kravchenko, K.
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Millour, F.
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Schaefer, G.
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Schultheis, M.
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Freytag, Bernd, ...
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show more...
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Creevey, O.
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Hocde, V.
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Morand, F.
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Ligi, R.
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Kraus, S.
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Monnier, J. D.
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Mourard, D.
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Nardetto, N.
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Anugu, N.
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Le Bouquin, J. - ...
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Davies, C. L.
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Ennis, J.
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Gardner, T.
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Labdon, A.
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Lanthermann, C.
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Setterholm, B. R ...
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ten Brummelaar, ...
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Uppsala University