CHARA/FLUOR updates and performance

Mérand, A.; Foresto, V. Coudé du; Kellerer, Aglae; Brummelaar, T. ten; Réess, Jean-Michel; Ziegler, D.

doi:10.1117/12.671045

Cited by 15 publications

(16 citation statements)

References 14 publications

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“…The observations were performed in June 2010 and August 2011 at the CHARA Array (ten Brummelaar et al 2005) in the nearinfrared K band (1.9 λ 2.3 μm) with the Fiber Linked Unit for Optical Recombination (FLUOR; Coudé du Foresto et al 2003;Mérand et al 2006a). For these observations, we used baselines longer than 200 m in order to resolve sufficiently well the two targets.…”

Section: Interferometric Observationsmentioning

confidence: 99%

“…The squared visibility of the fringes was estimated from the raw data using the FLUOR data reduction software (Coudé du Foresto et al 1997;Mérand et al 2006a), based on the integration of the fringe power spectrum. The raw squared visibilities were then calibrated using resolved calibrator stars, chosen from the catalogue of Mérand et al (2005a), using criteria defined to minimize the calibration bias and maximize the signalto-noise ratio.…”

Section: Interferometric Observationsmentioning

confidence: 99%

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Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae

Gallenne¹,

Kervella²,

Mérand³

et al. 2012

A&A

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We report the first angular diameter measurements of two classical Cepheids, FF Aql and T Vul, that we obtain using observations with the FLUOR instrument installed at the CHARA interferometric array. We derive average limb-darkened angular diameters of θ LD = 0.878 ± 0.013 mas and θ LD = 0.629 ± 0.013 mas, respectively, for FF Aql and T Vul. Combining these angular diameters with the HST-FGS trigonometric parallaxes leads to linear radii R = 33.6± 2.2 R and R = 35.6± 4.4 R , respectively. The comparison with empirical and theoretical period-radius relations leads to the conclusion that these Cepheids are pulsating in their fundamental mode. The knowledge of this pulsation mode is of prime importance to calibrating the period-luminosity relation with a uniform sample of fundamental mode Cepheids.

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Section: Interferometric Observationsmentioning

confidence: 99%

Section: Interferometric Observationsmentioning

confidence: 99%

Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae

Gallenne¹,

Kervella²,

Mérand³

et al. 2012

A&A

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“…Table 1). Right panel: transmission curve (dashed line) of the FLUOR (2.14 ± 0.26 μm) filter (Mérand et al 2006) mounted on CHARA. Colors and offsets are the same as in left panel.…”

Section: Three-dimensional Limb Darkening Coefficientsmentioning

confidence: 99%

Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for interpreting interferometric observations

Chiavassa¹,

Collet²,

Casagrande³

et al. 2010

A&A

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Context. Theoretical predictions from models of red giant branch stars are a valuable tool for various applications in astrophysics ranging from galactic chemical evolution to studies of exoplanetary systems. Aims. We use the radiative transfer code Optim3D and realistic 3D radiative-hydrodynamical (RHD) surface convection simulations of red giants to explore the impact of granulation on interferometric observables. We assess how 3D simulations of surface convection can be validated against observations. Methods. We computed intensity maps for the 3D simulation snapshots in two filters, the optical at 5000 ± 300 Å and the K band 2.14±0.26 μm FLUOR filter, corresponding to the wavelength-range of instruments mounted on the CHARA interferometer. From the intensity maps, we constructed images of the stellar disks and account for center-to-limb variations. We then derived interferometric visibility amplitudes and phases. We study their behavior with position angle and wavelength, and compare them with CHARA observations of the red giant star HD 214868. Results. We provide average limb darkening coefficients for different metallicities and wavelengths ranges. We explain prospects for detecting and characterizing granulation and center-to-limb variations of red giant stars with today's interferometers. Regarding interferometric observables, we find that the effect of convective-related surface structures depends on metallicity and surface gravity. We provide theoretical closure-phases that should be incorporated into the analysis of red giant planet companion closure phase signals. We estimate 3D−1D corrections to stellar radii determination: 3D models are ∼3.5% smaller to ∼1% larger in the optical than 1D, and roughly 0.5 to 1.5% smaller in the infrared. Even if these corrections are small, they are needed to properly set the zero point of effective temperature scale derived by interferometry and to strengthen the confidence of existing red giant catalogs of calibrating stars for interferometry. Finally, we show that our RHD simulations provide an excellent fit to the red giant HD 214868 even though more observations are needed at higher spatial frequencies and shorter wavelength.

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“…This instrument is equipped with a near infrared K band filter (1.9 ≤ λ ≤ 2.35 μm). We extracted the instrumental visibilities from the raw data using the FLUOR data reduction software (Coudé du Foresto et al 1997;Kervella et al 2004;Mérand 2006). For all the reported observations, we used the CHARA baselines S2-W2, with ground lengths of 177 m, which is mostly a northsouth baseline in orientation.…”

Section: Comparison Of Theoretical and Observed Frequenciesmentioning

confidence: 99%

Asteroseismology and interferometry of the red giant star ϵ Ophiuchi

Mazumdar

Mérand

Demarque

et al. 2009

A&A

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The GIII red giant star Oph has been found to exhibit several modes of oscillation by the MOST mission. We interpret the observed frequencies of oscillation in terms of theoretical radial p-mode frequencies of stellar models. Evolutionary models of this star, in both shell H-burning and core He-burning phases of evolution, are constructed using as constraints a combination of measurements from classical ground-based observations (for luminosity, temperature, and chemical composition) and seismic observations from MOST. Radial frequencies of models in either evolutionary phase can reproduce the observed frequency spectrum of Oph almost equally well. The best-fit models indicate a mass in the range of 1.85 ± 0.05 M with radius of 10.55 ± 0.15 R . We also obtain an independent estimate of the radius of Oph with highly accurate interferometric observations in the infrared K band, using the CHARA/FLUOR instrument. The measured limb-darkened disk angular diameter of Oph is 2.961 ± 0.007 mas. Together with the Hipparcos parallax, this translates into a photospheric radius of R = 10.39 ± 0.07 R . The radius obtained from the asteroseismic analysis matches the interferometric value quite closely even though the radius was not constrained during the modelling.

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CHARA/FLUOR updates and performance

Cited by 15 publications

References 14 publications

Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae

Mean angular diameters, distances, and pulsation modes of the classical Cepheids FF Aquilae and T Vulpeculae

Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for interpreting interferometric observations

Asteroseismology and interferometry of the red giant star ϵ Ophiuchi

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