The VLT Interferometer: a unique instrument for high-resolution astronomy

Glindemann, Andreas; Abuter, R.; Carbognani, F.; Delplancke, F.; Dérie, F.; Gennai, A.; Gitton, Philippe B.; Kervella, P.; Koehler, Bertrand; Lévêque, S.; Ménardi, Serge; Michel, Alain; Paresce, Francesco; Duc, Than Phan; Richichi, A.; Schoeller, Markus; Tarenghi, M.; Wallander, Anders; Wilhelm, Rainer

doi:10.1117/12.390163

Cited by 48 publications

(20 citation statements)

References 5 publications

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“…EX Lup was observed with the Mid-Infrared Interferometric Instrument (MIDI; Leinert et al 2003), the N-band instrument on the Very Large Telescope Interferometer (VLTI; Glindemann et al 2000). Spectrally resolved interferometric visibilities were obtained between 8 and 13 μm with a spectral resolution of R ≈ 35.…”

Section: Vlti Midimentioning

confidence: 99%

THE 2008 OUTBURST OF EX Lup—SILICATE CRYSTALS IN MOTION

Juhász

Dullemond

Boekel

et al. 2011

ApJ

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EX Lup is the prototype of the EXor class of eruptive young stars. These objects show optical outbursts which are thought to be related to runaway accretion onto the star. In a previous study we observed in situ crystal formation in the disk of EX Lup during its latest outburst in 2008, making the object an ideal laboratory to investigate circumstellar crystal formation and transport. This outburst was monitored by a campaign of ground-based and Spitzer Space Telescope observations. Here we modeled the spectral energy distribution (SED) of EX Lup in the outburst from optical to millimeter wavelengths with a two-dimensional radiative transfer code. Our results showed that the shape of the SED at optical wavelengths was more consistent with a single-temperature blackbody than a temperature distribution. We also found that this single-temperature component emitted 80%-100% of the total accretion luminosity. We concluded that a thermal instability, the most widely accepted model of EXor outbursts, was likely not the triggering mechanism of the 2008 outburst of EX Lup. Our mid-infrared Spitzer spectra revealed that the strength of all crystalline bands between 8 and 30 μm increased right after the end of the outburst. Six months later, however, the crystallinity in the 10 μm silicate feature complex decreased. Our modeling of the mid-infrared spectral evolution of EX Lup showed that, although vertical mixing should be stronger during the outburst than in the quiescent phase, fast radial transport of crystals (e.g., by stellar/disk wind) was required to reproduce the observed mid-infrared spectra.

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Section: Vlti Midimentioning

confidence: 99%

THE 2008 OUTBURST OF EX Lup—SILICATE CRYSTALS IN MOTION

Juhász

Dullemond

Boekel

et al. 2011

ApJ

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“…Leinert et al 2003) on the VLT-I (e.g. Glindemann et al 2000) in Science Demonstration Time (SDT) on November 8 and 10, 2003. The interferometric data will be presented and analysed in a forthcoming paper, together with additional MIDI observations scheduled for autumn 2005 which will cover a wider range in spatial frequencies.…”

Section: Interferometrymentioning

confidence: 99%

Amorphous alumina in the extended atmosphere of α Orionis

Verhoelst

Decin²,

Malderen³

et al. 2006

A&A

111

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In this paper we study the extended atmosphere of the late-type supergiant α Orionis. Infrared spectroscopy of red supergiants reveals strong molecular bands, some of which do not originate in the photosphere but in a cooler layer of molecular material above it. Lately, these layers have been spatially resolved by near and mid-IR interferometry. In this paper, we try to reconcile the IR interferometric and ISO-SWS spectroscopic results on α Orionis with a thorough modelling of the photosphere, molecular layer(s) and dust shell. From the ISO and near-IR interferometric observations, we find that α Orionis has only a very low density water layer close above the photosphere. However, mid-IR interferometric observations and a narrow-slit N-band spectrum suggest much larger extra-photospheric opacity close to the photosphere at those wavelengths, even when taking into account the detached dust shell. We argue that this cannot be due to the water layer, and that another source of mid-IR opacity must be present. We show that this opacity source is probably neither molecular nor chromospheric. Rather, we present amorphous alumina (Al 2 O 3 ) as the best candidate and discuss this hypothesis in the framework of dust-condensation scenarios.

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“…Lachaume@obs.ujf-grenoble.fr Recently, the Palomar Testbed Interferometer (PTI, Colavita et al 1999) and the Infrared Optical Telescope Array (IOTA, Carleton et al 1994) allowed us to probe circumstellar matter in star-forming regions (Malbet et al 1998;Akeson et al 2000;Malbet & Berger 2002b;Akeson et al 2002), giving some constraints on the geometry of these objects. With the advent of the Very Large Telescope Interferometre (VLTI, Glindemann et al 2000) and the (KI, Colavita 2001) we are expecting a much higher accuracy with their large pupils (8-10 m), and good constraints on objects thanks to the number of baselines available and partial phase information; yet they will not allow direct image reconstruction very soon because recombination will be first performed with two or three telescopes. The Navy Prototype Optical Interferometre (NPOI, Armstrong et al 1998), the CHARA array (ten Brummelaar et al 2000), and the Cambridge Optical Aperture Synthesis Interferometer (COAST, Haniff et al 2000) provide imaging capacities with a multi-telescope recombination, but with a lower sensitivity that renders faint object science difficult.…”

Section: Introductionmentioning

confidence: 99%

On marginally resolved objects in optical interferometry

Lachaume

2003

A&A

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Abstract.With the present and soon-to-be breakthrough of optical interferometry, countless objects shall be within reach of interferometers; yet, most of them are expected to remain only marginally resolved with hectometric baselines. In this paper, we tackle the problem of deriving the properties of a marginally resolved object from its optical visibilities. We show that they depend on the moments of flux distribution of the object: centre, mean angular size, asymmetry, and curtosis. We also point out that the visibility amplitude is a second-order phenomenon, whereas the phase is a combination of a first-order term, giving the location of the photocentre, and a third-order term, more difficult to detect than the visibility amplitude, giving an asymmetry coefficient of the object. We then demonstrate that optical visibilities are not a good model constraint while the object stays marginally resolved, unless observations are carried out at different wavelengths. Finally, we show an application of this formalism to circumstellar discs.

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The VLT Interferometer: a unique instrument for high-resolution astronomy

Cited by 48 publications

References 5 publications

THE 2008 OUTBURST OF EX Lup—SILICATE CRYSTALS IN MOTION

THE 2008 OUTBURST OF EX Lup—SILICATE CRYSTALS IN MOTION

Amorphous alumina in the extended atmosphere of α Orionis

On marginally resolved objects in optical interferometry

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