Fringe tracking performance monitoring: FINITO at VLTI

Mérand, A.; Patru, Fabien; Berger, J.‐P.; Percheron, Isabelle; Poupar, Sébastien

doi:10.1117/12.925450

Cited by 7 publications

(6 citation statements)

References 7 publications

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“…Because of the high brightness of the K-M giants, observed with good weather conditions (0."7-1. "2 seeing), the low-contrast fringes (for each of three baselines) were detected without the use of VLTI fringe tracker FINITO (Mérand et al 2012). So, the measurements have been performed with a Detector Integration Time (DIT) of 0.12s and 500 exposures.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER

Hadjara

Cruzalèbes

Nitschelm

et al. 2019

Monthly Notices of the Royal Astronomical Society

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We determine the physical parameters of the outer atmosphere of a sample of eight evolved stars, including the Red SuperGiant α Sco, the Red Giant Branch stars α Boo and γ Cru, the K giant λ Vel, the normal M-giants BK Vir and SW Vir, and the Mira star W Hya (in two different luminosity phases) by spatially resolving the stars in the individual carbon monoxide (CO) first overtone lines. We used the AM-BER (Astronomical Multi-BEam combineR) instrument at the Very Large Telescope Interferometer (VLTI), in high-resolution mode (λ/∆λ ≈ 12000) between 2.28 and 2.31 µm in K-band. The maximal angular resolution is 10 mas, obtained by triplets telescope configuration, with baselines from 7 to 48 m. By using a numerical model of a molecular atmosphere in spherical shells (MOLsphere), named PAMPERO (for Physical Approach of Molecular Photospheric Ejection at high-angular-Resolution for evOlved-stars) we add multiple extended CO layers above the photospheric MARCS model at an adequate spatial resolution. We use the differential visibilities and the spectrum to estimate the size (R) of the CO MOLsphere, its column density (N CO ) and temperature (T mol ) distributions along the stellar radius. The combining of the χ2 minimization and a fine grid approach for uncertainty analysis leads to reasonable N CO and T mol distributions along the stellar radius of the MOLsphere.

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Section: Observations and Data Reductionmentioning

confidence: 99%

A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER

Hadjara

Cruzalèbes

Nitschelm

et al. 2019

Monthly Notices of the Royal Astronomical Society

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“…Regulus was observed with the AMBER/VLTI instrument located at Cerro Paranal, Chile, with the Auxiliary Telescopes. The fringes were stabilized using FINITO (Fringetracking Instrument of NIce and TOrino) (Mérand et al 2012) as a fringe tracker, allowing us to use a Detector Integration Time DIT=3sec for 20 exposures. The observations have been performed using the high spectral resolution mode of AMBER (λ/δλ ≈ 12000).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Differential interferometry of the rapid rotator Regulus

Hadjara

Petrov

Jankov

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We analyse interferometric data obtained for Regulus with AMBER (Astronomical Multi-BEam combineR) at high spectral resolution (λ/δλ ≈ 12000) across the Brγ spectral line. The study of the photocentre displacement allows us to constrain a large number of stellar parameters -equatorial radius R eq , equatorial velocity V eq , inclination i, rotation-axis position angle P A rot , and flattening -with an estimation of gravity-darkening coefficient β using previously published theoretical results. We use the Simulation Code of Interferometric-observations for ROtators and CirCumstellar Objects (SCIROCCO), a semi-analytical algorithm dedicated to fast rotators. We chose Regulus because it is a very well-known edge-on star, for which an alternative approach is needed to check the previously published results. Our analysis showed that a significant degeneracy of solution is present. By confronting the results obtained by differential interferometry with those obtained by conventional long-base interferometry, we obtain similar results (within the uncertainties), thereby validating our approach, where V eq and i are found separately. From the photocentre displacement, we can independently deduce P A rot . We use two minimization methods to restrict observed stellar parameters via a fast rotator model: a non-stochastic method (χ 2 fit) and a stochastic one (Markov Chain Monte Carlo method), in order to check whether the correct global minimum is achieved particularly with respect to the degeneracies of the gravity darkening parameter β, where we demonstrate, using a quantitative analysis of parameters, that the estimate of β is easier for stars with an inclination angle of around 45 • .

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“…This can lead to visibility calibrations of low quality. Therefore, we used the VLTI Reflective Memory Network Recorder (RMNrec) data (Le Bouquin et al 2009;Mérand et al 2012) to improve the visibility calibration by rejecting 46% of the exposures that showed a disagreement between the RMNrec values of calibrator and science object.…”

Section: Observations and Data Processingmentioning

confidence: 99%

VLTI-AMBER velocity-resolved aperture-synthesis imaging ofηCarinae with a spectral resolution of 12 000

Weigelt

Hofmann

Schertl

et al. 2016

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Context. The mass loss from massive stars is not understood well. η Carinae is a unique object for studying the massive stellar wind during the luminous blue variable phase. It is also an eccentric binary with a period of 5.54 yr. The nature of both stars is uncertain, although we know from X-ray studies that there is a wind-wind collision whose properties change with orbital phase. Aims. We want to investigate the structure and kinematics of η Car's primary star wind and wind-wind collision zone with a high spatial resolution of ∼6 mas (∼14 au) and high spectral resolution of R = 12 000. Methods. Observations of η Car were carried out with the ESO Very Large Telescope Interferometer (VLTI) and the AMBER instrument between approximately five and seven months before the August 2014 periastron passage. Velocity-resolved aperture-synthesis images were reconstructed from the spectrally dispersed interferograms. Interferometric studies can provide information on the binary orbit, the primary wind, and the wind collision.Results. We present velocity-resolved aperture-synthesis images reconstructed in more than 100 different spectral channels distributed across the Brγ 2.166 µm emission line. The intensity distribution of the images strongly depends on wavelength. At wavelengths corresponding to radial velocities of approximately −140 to −376 km s −1 measured relative to line center, the intensity distribution has a fan-shaped structure. At the velocity of −277 km s −1 , the position angle of the symmetry axis of the fan is ∼126 • . The fan-shaped structure extends approximately 8.0 mas (∼18.8 au) to the southeast and 5.8 mas (∼13.6 au) to the northwest, measured along the symmetry axis at the 16% intensity contour. The shape of the intensity distributions suggests that the obtained images are the first direct images of the innermost wind-wind collision zone. Therefore, the observations provide velocity-dependent image structures that can be used to test three-dimensional hydrodynamical, radiative transfer models of the massive interacting winds of η Car.

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Fringe tracking performance monitoring: FINITO at VLTI

Cited by 7 publications

References 7 publications

A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER

A CO-multilayer outer atmosphere for eight evolved stars revealed with VLTI/AMBER

Differential interferometry of the rapid rotator Regulus

VLTI-AMBER velocity-resolved aperture-synthesis imaging ofηCarinae with a spectral resolution of 12 000

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