MACAO-VLTI: an adaptive optics system for the ESO interferometer

Arsenault, Robin; Alonso, Jaime; Bonnet, Henri; Brynnel, Joar; Délabre, Bernard; Donaldson, Robert H.; Dupuy, Christophe; Fedrigo, Enrico; Farinato, Jacopo; Hubin, N.; Ivanescu, Liviu; Kasper, Markus; Paufique, J.; Rossi, Silvio; Tordo, Sebastien; Stroebele, Stefan; Lizon, J. L.; Gigan, P.; Delplancke, F.; Silber, A.; Quattri, M.; Reiss, Roland

doi:10.1117/12.458836

Cited by 52 publications

(32 citation statements)

References 7 publications

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“…The present reprocessing is intended to ensure the consistency of the visibilities with the more recent observations. The 2004 observations were obtained with natural seeing, while the 2006 observations employed the MACAO adaptive optics system (Arsenault et al 2003), that provides an improved stability of the photometry in MIDI.…”

Section: Midi Observationsmentioning

confidence: 99%

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

Kervella¹,

Mérand

Gallenne

2009

A&A

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Context. Compact circumstellar envelopes (CSEs) have been detected around several Cepheids by interferometry. In particular, observations with the VINCI instrument revealed in 2006 a compact envelope around the long period Cepheid Car (P = 35.5 days). Another Cepheid, RS Pup (P = 41.4 days), presents a large (≈2 ) circumstellar nebula scattering the Cepheid light in the visible. These envelopes are particularly interesting for two reasons: their presence could impact the Cepheid distance scale, and they could imply stellar mass loss. Aims. Our goal is to establish the spatial and spectral properties of the CSEs of Car and RS Pup. This is done through a parametrization of the envelopes in terms of fractional flux (with respect to the star) and angular size. Methods. We retrieved archival Spitzer images of the two stars (λ = 3.5−70 μm), and obtained new diffraction-limited imaging with the VLT/VISIR camera in BURST mode (λ = 8.6−11.9 μm), as well as interferometric observations with the VLTI/MIDI beam combiner (λ = 8−13 μm). This combination of single-telescope and interferometric techniques allows us to probe the envelopes of the two Cepheids over a broad range of angular scales, from arcminutes to milliarcseconds. Results. The circumstellar envelope of RS Pup is resolved spatially at 24 and 70 μm by Spitzer, and around 10 μm by MIDI and VISIR. The envelope of Car appears much more compact, and is resolved only in the VISIR and MIDI observations. The infrared excesses we detect around RS Pup and Car are both very significant, but differ considerably in spectral and spatial properties. We detect a warm component in the CSE of both stars at a spatial scale of a few 100 to a few 1000 AU. In addition, RS Pup presents a very large (several 100 000 AU) and cold (≈40 K) dusty envelope. Conclusions. The observed properties of the CSEs lead us to propose that the cold dust content of the large reflection nebula surrounding RS Pup has an interstellar origin, while the warm CSEs of the two stars were created by ongoing stellar mass loss. We also speculate that the NGC 7023 reflection nebula surrounding the Herbig Be star HD 200775 is an analogue of RS Pup at an age of 100 000 years. The presence of CSEs around the two brightest long-period Cepheids is an indication that many long-period members of this class, if not all, could be surrounded by warm circumstellar envelopes created by mass loss. However, very large dusty envelopes such as that of RS Pup are probably less common, as according to our scenario, they require the presence of a high dust density in the interstellar medium (ISM) at the time of the formation of the Cepheid progenitor.

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Section: Midi Observationsmentioning

confidence: 99%

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

Kervella¹,

Mérand

Gallenne

2009

A&A

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“…Cross-correlating with a model spectrum combining CO with H 2 O and CH 4 does not give an improvement over the signal from CO alone. 3 The result of the CO cross-correlation is shown in Figure 1. Due to the orbital velocity of the planet, of which the radial component changes during the transit, the CO-signal shifts in position from the beginning to the end of the transit by ~30 km sec -1 .…”

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confidence: 99%

“…2 spectrograph CRIRES 2 , located at the Nasmyth A focus of UT1, making use of the Multi-Application Curvature Adaptive Optics system MACAO 3 .…”

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confidence: 99%

The orbital motion, absolute mass and high-altitude winds of exoplanet HD 209458b

Snellen

Kok

Mooij

et al. 2010

Nature

732

836

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For extrasolar planets discovered using the radial velocity method 1 , the spectral characterization of the host star leads to a mass-estimate of the star and subsequently of the orbiting planet. In contrast, if also the orbital velocity of the planet would be known, the masses of both star and planet could be determined We obtained 51 spectra with a wavelength coverage of 2291 to 2349 nm at a spectral resolution of 100,000. For a detailed description of the observational set-up and data reduction we refer the reader to the supplementary information. During the transit, star-light filters through the atmosphere of the planet, leaving an imprint of molecular absorption lines in the spectrum. In the observed wavelength regime, 56 strong spectral lines from carbon monoxide are expected to be present, and we extracted the CO-signal by cross-correlating a CO model-spectrum with the observed data. We developed our own transmission model to calculate the expected CO-spectrum, with the planet atmosphere described by one mean profile that is in hydrostatic equilibrium (see the supplementary information for details). In our initial model, the temperature is based on the best-fit day-side temperature profile 4 for HD209458b, and gases are uniformly mixed with volume mixing-ratios of 2x10 -4 (CH 4 and CO) and 5x10 -4 (H 2 O) as based on the case 5,6 of HD189733b.The observed spectra are completely dominated by numerous telluric absorption lines, caused mainly by methane and water vapour in the Earth's atmosphere 7 . The depths of these lines vary with airmass, and an important part of the data reduction process therefore involves the removal of this telluric contamination. Residual effects, clearly present at the positions of strong telluric lines, are further suppressed by normalizing each pixel value in a spectrum by its variance over time. Although this may in certain places also suppress carbon monoxide lines, it prevents the cross-correlation signal to be dominated by telluric residuals. Our analysis results in the significant detection of a CO signal and detection of the orbital motion of the planet. Similar crosscorrelation analyses with H 2 O and CH 4 templates did not result in detections. The model transmission spectrum of CH 4 is so densely packed with lines that it strongly hampers a cross-correlation analysis. Two CH 4 lines are significantly stronger than the others, but unfortunately one falls in a gap between two of the detector arrays. Cross-correlating with a model spectrum combining CO with H 2 O and CH 4 does not give an improvement over the signal from CO alone. The result of the CO cross-correlation is shown in Figure 1. Due to the orbital velocity of the planet, of which the radial component changes during the transit, the CO-signal shifts in position from the beginning to the end of the transit by ~30 km sec -1 .As shown in Figure 2, from this shift we derive the planet orbital velocity to be v p = 140 ± 10 km sec -1 (1σ), corresponding to the maximum radial velocity at quadrature. In combination wit...

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“…To reach a sufficient sensitivity, ESO provided a 60 actuator curvature sensing system MACAO (Multi-Application Curvature Adaptive Optics) (Arsenault et al 2003) specified to deliver at least a 50% Strehl ratio @ 2.2 µm for on-axis bright sources (V = 8) under median seeing conditions (0.65 ) and a 25% Strehl ratio @ 2.2 µm for faint sources (V = 15.5) under the same seeing conditions. The required high accuracy of the absolute visibility measurements implies the use of spatial filters (Mège et al 2000;Tatulli et al 2004) with single mode fibers based on the experience of other smaller, successful interferometers such as IOTA/FLUOR (Coudé du Foresto 1997).…”

Section: Introductionmentioning

confidence: 99%

Optical configuration and analysis of the AMBER/VLTI instrument

Robbe-Dubois¹,

Lagarde

Petrov³

et al. 2007

A&A

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Aims. This paper describes the design goals and engineering efforts that led to the realization of AMBER (Astronomical Multi BEam combineR) and to the achievement of its present performance. Methods. On the basis of the general instrumental concept, AMBER was decomposed into modules whose functions and detailed characteristics are given. Emphasis is put on the spatial filtering system, a key element of the instrument. We established a budget for transmission and contrast degradation through the different modules, and made the detailed optical design. The latter confirmed the overall performance of the instrument and defined the exact implementation of the AMBER optics. Results. The performance was assessed with laboratory measurements and commissionings at the VLTI, in terms of spectral coverage and resolution, instrumental contrast higher than 0.80, minimum magnitude of 11 in K, absolute visibility accuracy of 1%, and differential phase stability of 10 −3 rad over one minute.

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MACAO-VLTI: an adaptive optics system for the ESO interferometer

Cited by 52 publications

References 7 publications

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

The circumstellar envelopes of the Cepheids $\mathsf{\ell}$ Carinae and RS Puppis

The orbital motion, absolute mass and high-altitude winds of exoplanet HD 209458b

Optical configuration and analysis of the AMBER/VLTI instrument

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