The limb-darkened Arcturus: imaging with the IOTA/IONIC interferometer

Lacour, S.; Meimon, Serge; Thiébaut, Éric; Perrin, G.; Verhoelst, Tijl; Pedretti, E.; Schuller, P. A.; Mugnier, Laurent M.; Monnier, John D.; Berger, J.‐P.; Haubois, X.; Poncelet, A.; Besnerais, Guy Le; Eriksson, K.; Millan-Gabet, R.; Ragland, Sam; Lacasse, M. G.; Traub, Wesley A.

doi:10.1051/0004-6361:200809611

Cited by 53 publications

(51 citation statements)

References 42 publications

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“…T eff = 4303 ± 47 (Quirrenbach et al 1996), 4290 ± 30 (Griffin & Lynas-Gray 1999), and 4295 ± 26 K (Lacour et al 2008). We adopt the last value in the following.…”

Section: Physical Parametersmentioning

confidence: 99%

Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields

Morel

Miglio

Lagarde

et al. 2014

A&A

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A precise characterisation of the red giants in the seismology fields of the CoRoT satellite is a prerequisite for further in-depth seismic modelling. High-resolution FEROS and HARPS spectra were obtained as part of the ground-based follow-up campaigns for 19 targets holding great asteroseismic potential. These data are used to accurately estimate their fundamental parameters and the abundances of 16 chemical species in a self-consistent manner. Some powerful probes of mixing are investigated (the Li and CNO abundances, as well as the carbon isotopic ratio in a few cases). The information provided by the spectroscopic and seismic data is combined to provide more accurate physical parameters and abundances. The stars in our sample follow the general abundance trends as a function of the metallicity observed in stars of the Galactic disk. After an allowance is made for the chemical evolution of the interstellar medium, the observational signature of internal mixing phenomena is revealed through the detection at the stellar surface of the products of the CN cycle. A contamination by NeNa-cycled material in the most massive stars is also discussed. With the asteroseismic constraints, these data will pave the way for a detailed theoretical investigation of the physical processes responsible for the transport of chemical elements in evolved, low-and intermediate-mass stars.

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“…T eff = 4303 ± 47 (Quirrenbach et al 1996), 4290 ± 30 (Griffin & Lynas-Gray 1999), and 4295 ± 26 K (Lacour et al 2008). We adopt the last value in the following.…”

Section: Physical Parametersmentioning

confidence: 99%

Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields

Morel

Miglio

Lagarde

et al. 2014

A&A

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“…In this paper we used two of them: MIRA and WISARD. Both are presented and compared in Le Besnerais (2008) and in Lacour et al (2008). The major advantage of such methods is that they can reveal structures by reconstructing an image which fits the data and which is also close to an a priori image of the object.…”

Section: Image Reconstruction and Asymmetriesmentioning

confidence: 99%

Imaging the spotty surface of Betelgeuse in theHband

Haubois¹,

Perrin²,

Lacour³

et al. 2009

A&A

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158

171

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Aims. This paper reports on H-band interferometric observations of Betelgeuse made at the three-telescope interferometer IOTA. We image Betelgeuse and its asymmetries to understand the spatial variation of the photosphere, including its diameter, limb darkening, effective temperature, surrounding brightness, and bright (or dark) star spots. Methods. We used different theoretical simulations of the photosphere and dusty environment to model the visibility data. We made images with parametric modeling and two image reconstruction algorithms: MIRA and WISARD. Results. We measure an average limb-darkened diameter of 44.28 ± 0.15 mas with linear and quadratic models and a Rosseland diameter of 45.03 ± 0.12 mas with a MARCS model. These measurements lead us to derive an updated effective temperature of 3600 ± 66 K. We detect a fully-resolved environment to which the silicate dust shell is likely to contribute. By using two imaging reconstruction algorithms, we unveiled two bright spots on the surface of Betelgeuse. One spot has a diameter of about 11 mas and accounts for about 8.5% of the total flux. The second one is unresolved (diameter < 9 mas) with 4.5% of the total flux. Conclusions. Resolved images of Betelgeuse in the H band are asymmetric at the level of a few percent. The MOLsphere is not detected in this wavelength range. The amount of measured limb-darkening is in good agreement with model predictions. The two spots imaged at the surface of the star are potential signatures of convective cells.

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“…Owing to the large apparent diameter of Arcturus (21.05 ± 0.21 mas), Lacour et al (2008) attempted to directly image its surface via interferometry, using a technique similar to that successfully applied to Altair (α Aql) by Monnier et al (2007) with a resolution of <1 mas. They failed to detect surface inhomogeneities, and concluded that the most probable brightness distribution is that of a simple limb-darkened disk.…”

Section: Possible Magnetic Field Generatorsmentioning

confidence: 99%

First detection of a weak magnetic field on the giant Arcturus: remnants of a solar dynamo?

Sennhauser

Berdyugina

2011

A&A

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Context. Arcturus is the second closest K giant and among the brightest stars in the sky. It has not been found to have a magnetic field, even though Ca ii H&K lines as activity indicators imply that Arcturus is magnetically active. Aims. We measure the mean longitudinal magnetic field strengths and interpret them in terms of an intraseasonal activity modulation. Methods. We apply our new Zeeman component decomposition (ZCD) technique to three single sets of Stokes I and V spectra to measure the longitudinal component of the magnetic field responsible for tiny Zeeman signatures detected in spectral line profiles. Results. For two of the spectra, we report the detection of the Zeeman signature of a weak longitudinal magnetic field of 0.65 ± 0.26 G and 0.43 ± 0.16 G. The third measurement is less significant, but all the measurements closely reproduce a rotationally modulated activity cycle with four active longitudes. Conclusions. For the first time, a magnetic field on Arcturus is directly detected. This field can be attributed to a diminishing solartype αΩ-dynamo acting in the deepening convection zone of Arcturus. We demonstrate that our new method ZCD lowers the detection limit of very weak magnetic fields from spectropolarimetric measurements.

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The limb-darkened Arcturus: imaging with the IOTA/IONIC interferometer

Cited by 53 publications

References 42 publications

Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields

Atmospheric parameters and chemical properties of red giants in the CoRoT asteroseismology fields

Imaging the spotty surface of Betelgeuse in theHband

First detection of a weak magnetic field on the giant Arcturus: remnants of a solar dynamo?

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