PurposeThe aim of this work is the development and characterization of a model observer (MO) based on convolutional neural networks (CNNs), trained to mimic human observers in image evaluation in terms of detection and localization of low-contrast objects in CT scans acquired on a reference phantom. The final goal is automatic image quality evaluation and CT protocol optimization to fulfill the ALARA principle.ApproachPreliminary work was carried out to collect localization confidence ratings of human observers for signal presence/absence from a dataset of 30,000 CT images acquired on a PolyMethyl MethAcrylate phantom containing inserts filled with iodinated contrast media at different concentrations. The collected data were used to generate the labels for the training of the artificial neural networks. We developed and compared two CNN architectures based respectively on Unet and MobileNetV2, specifically adapted to achieve the double tasks of classification and localization. The CNN evaluation was performed by computing the area under localization-ROC curve (LAUC) and accuracy metrics on the test dataset.ResultsThe mean of absolute percentage error between the LAUC of the human observer and MO was found to be below 5% for the most significative test data subsets. An elevated inter-rater agreement was achieved in terms of S-statistics and other common statistical indices.ConclusionsVery good agreement was measured between the human observer and MO, as well as between the performance of the two algorithms. Therefore, this work is highly supportive of the feasibility of employing CNN-MO combined with a specifically designed phantom for CT protocol optimization programs.
The first generation of ELT instruments includes an optical-infrared high resolution spectrograph, indicated as ELT-HIRES and recently christened ANDES (ArmazoNes high Dispersion Echelle Spectrograph). ANDES consists of three fibre-fed spectrographs (UBV, RIZ, YJH) providing a spectral resolution of ∼100,000 with a minimum simultaneous wavelength coverage of 0.4-1.8 µm with the goal of extending it to 0.35-2.4 µm with the addition of a K band spectrograph. It operates both in seeing- and diffraction-limited conditions and the fibre-feeding allows several, interchangeable observing modes including a single conjugated adaptive optics module and a small diffraction-limited integral field unit in the NIR. Its modularity will ensure that ANDES can be placed entirely on the ELT Nasmyth platform, if enough mass and volume is available, or partly in the Coudé room. ANDES has a wide range of groundbreaking science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars, tests on the stability of Nature’s fundamental couplings, and the direct detection of the cosmic acceleration. The ANDES project is carried forward by a large international consortium, composed of 35 Institutes from 13 countries, forming a team of more than 200 scientists and engineers which represent the majority of the scientific and technical expertise in the field among ESO member states.
At the end of 2021, the ESO council approved the start of the construction phase for a High Resolution Spectrograph for the ELT, formerly known as ELT-HIRES, renamed recently as ANDES (ArmazoNes high Dispersion Echelle Spectrograph). The current initial schedule foresees a 9-years development aimed to bring the instrument on-sky soon after the first-generation ELT instruments. ANDES combines high spectral resolution (up to 100,000), wide spectral range (0.4 µm to 1.8 µm with a goal from 0.35 µm to 2.4 µm) and extreme stability in wavelength calibration accuracy (better than 0.02 m/s rms over a 10-year period in a selected wavelength range) with massive optical collecting power of the ELT thus enabling to achieve possible breakthrough groundbreaking scientific discoveries. The main science cases cover a possible detection of life signatures in exoplanets, the study of the stability of Nature’s physical constants along the universe lifetime and a first direct measurement of the cosmic acceleration. The reference design of this instrument in its extended version (with goals included) foresees 4 spectrographic modules fed by fibers, operating in seeing and diffraction limited (adaptive optics assisted) mode carried out by an international consortium composed by 24 institutes from 13 countries which poses big challenges in several areas. In this paper we will describe the approach we intend to pursue to master management and system engineering aspects of this challenging instrument focused mainly on the preliminary design phase, but looking also ahead towards its final construction.
HIRES is the high-resolution spectrograph of the European Extremely Large Telescope at optical and near-infrared wavelengths. It consists of three fibre-fed spectrographs providing a wavelength coverage of 0.4-1.8 µm (goal 0.35-2.4 µm) at a spectral resolution of 100,000. The fibre-feeding allows HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU in the NIR. Therefore, it will be able to operate both in seeing- and diffraction-limited modes. Its modularity will ensure that HIRES can be placed entirely on the Nasmyth platform, if enough mass and volume is available, or part on the Nasmyth and part in the Coud`e room. ELT-HIRES has a wide range of science cases spanning nearly all areas of research in astrophysics and even fundamental physics. Among the top science cases there are the detection of biosignatures from exoplanet atmospheres, finding the fingerprints of the first generation of stars (PopIII), tests on the stability of Nature’s fundamental couplings, and the direct detection of the cosmic acceleration. The HIRES consortium is composed of more than 30 institutes from 14 countries, forming a team of more than 200 scientists and engineers.
The HIRES-ELT instrument foresees an observing mode that delivers integral field high resolution spectroscopy with spatial sampling down to the diffraction limit of the ELT telescope. The IFU-SCAO module presented here is sub-system of the front-end of HIRES-ELT that includes two modules: SCAO and IFU. The first is the wavefront sensor, based on a pyramid beam-splitter, that provides the guiding on the reference star and the analysis of the incoming wavefront; the second is the module that transforms the incoming f/17.7 light beam from the telescope to the appropriate f/numbers to feed the spectrometer fibers-array with the required spatial scale. In this paper, we will present the SCAO optical design to allow the exoplanet atmosphere detection in reflection. To achieve this goal, we studied a feasible pyramid wavefront sensor to be inserted in a sliding arm of the HIRES front end. The CCD camera is based on a CCD220 chip in which will be imaged the telescope pupil, sampled with a 90x90 sub-aperture grid. A total of 4089 Karhunen-Loeve modes have been generated and used to close an end-to-end simulation. The AO loop runs up to 1000 KHz and it allows to shrink the PSF to the diffraction limits of the telescope ant to achieve Strehl Ratio (SR) above 70% in best seeing case up to magnitude 15 in H-band and a SR permanently above 40%, same band, up to magnitude 14 in case of median seeing. For λ=1600nm the 50% of energy is reached before 1 λ/D for all the plotted I-magnitude under the best seeing conditions. Under Median seeing conditions, the 50% is reached before 2λ/D up to I-mag 13. For λ=1000nm instead, we reach the 50% of encircled energy before a radius of 2λ/D for I-mag less than 14 and after 5λ/D for I-mag greater than 15 in the best seeing case. For each IFU spatial sampling and resolution, we can reach a contrast of 103 at a distance of 4 spaxels from central peak.
HIRES is a high-resolution spectrograph to me mounted on one of the Nasmyth foci of the ESO Extremely Large Telescope in Chile. This instrument will be composed by up to four Spectrograph to cover a high spectral range: one for the U band, one for the BVRI band, one for the ZYJH band, and one for the K band. To stabilize and inject the light coming from the telescope into the different spectrographs a Front End will be installed on the Nasmyth focus. In this paper, the design of the HIRES Front End will be presented. It will be composed by a structure, a cable derotator and four benches: two for the Observation mode, one for the Polarimeter arm, and one for the IFU/SCAO. Due to the absence of an interface flange with the telescope the cable derotator will directly support the four benches, positioning them in operation or standby mode. Moreover, due to the different requirements, the cables bundles will be split and derotated in different ways: part of them using different wheels, part of them twisting the cables. For the most critical ones, the electronic will be directly integrated on the derotator system. The preliminary optical and optomechanical design of the observing mode arm will be detailed also showing the techniques used to maximize the modularity of the four sub-Front End modules in order to decrease the Mean Time To Repair and allow for future upgrades or modifications on the single bands.
We present an application of the HIRES End-to-End (E2E) simulator and HIRES Exposure Time Calculator (ETC) to derive a more detailed behavior of the spectrograph efficiency by including physical modeling of diffraction at the echelle grating and the cross-disperser. The result will be used with the Spectral Energy Distributions of calibration lights for wavelength solutions and flat fielding to quantitatively characterize the spectrograph in terms of achieved accuracy. By showing the contribution of photon noise, detector noise and cross talk between adjacent fibers we discuss methods that could be used to determine the overall performance of the instrument, in term of the capability of photon collection as well as especially on the achieved precision on wavelength calibration that translates directly in radial velocity accuracy of the scientific light.
We present the updated design and architecture of the End-to-End simulator model of the high resolution spectrograph HIRES for the future Extremely Large Telescope (ELT). The model allows to simulate the propagation of photons starting from the scientific object of interest up to the detector, allowing to evaluate the performance impact of the different parameters in the spectrograph design. The model also includes a calibration light module, suitable to evaluate data reduction requirements. In this paper, we will detail the architecture of the simulator and the computational model which are strongly characterized by modularity and flexibility that will be crucial in the next generation instrumentation for projects such as the ELT due to of the high complexity and long-time design and development. We also highlight the Cloud Computing Architecture adopted for this software based on Amazon Web Services (AWS). We also present synthetic images obtained with the current version of the End-to-End simulator based on the requirements for ELTHIRES (especially high radial velocity accuracy) that are then ingested in the Data reduction Software (DRS) of CRIRES+ as case study.
The Phase A study for the high-resolution spectrograph for the Extremely Large Telescope (ELT-HIRES) has been concluded in late 2017. We present the main outcome for a polarimetric light feed from the intermediate focus (IF) and a Nasmyth focus of the telescope. We conclude that the use of the IF is mandatory for high-precision spectropolarimetry. Among the description of the product tree, we present phase-A level opto-mechanical designs of the subunits, describe the observational and calibration modes, the PSF error budget, and the preliminary FEM structural and earthquake analysis.
An update on the development of a ray tracing polarimetric simulator to estimate the instrumental polarization including both the telescope mirrors and the optical elements of the polarimeter is reported. Trade-off strategies and ongoing solutions in view of the Phase B are outlined too.
ELT-HIRES is the high resolution and ultra-stable Echelle spectrograph for the ELT. It has been conceived as a modular instrument provided with two independent spectrometers (the baseline design) and a possible extension to four, each of them optimized to cover a fixed spectral range. The role of the fibers is essential to provide the required ultrastability. Placed at the Nasmyth focus of the ELT, the HIRES fiber link transfers the light from the focal plane to the spectrographs. Each observing modes will be use a unique and independent group of fibers (bundle). The HIRES modular design makes it possible to have new observing modes just with the addition, removal or change of the specific bundles. From a functional point of view the HIRES fiber link subsystem performs some other important tasks, such as dicing the field of view, improving the system stability and providing a uniformly illuminated slit for spectrographs. It is a key subsystem for the instrument and represents a significant technological challenge. The technical requirements, conceptual design and technologies to be used are discussed in this paper. The current status of the subsystem, and future plans are also addressed.
The first generation of ELT instruments will include an optical-infrared High Resolution Spectrograph, conventionally indicated as ELT-HIRES. This paper describes the optical design and overall architecture of the instrument whose main capabilities can be summarized as follows. – Fibers fed specrographs with resolving power R=100,000 (HR-modes), R=150,000 (UHR-modes) and R=20,000 (MR-modes). – Simultaneous wavelength coverage from 400 nm to 1800 nm; extendable to 300-2400 nm. – Spectrometers with fixed configurations and without moving optical parts. – Maximum size of entrance apertures ideal for seeing limited observations. – Many observing modes, including seeing-limited single-object spectroscopy, multi-objects medium resolution spectroscopy and IFU observations with different spatial scales, down to the diffraction limit of the ELT telescope. – Observing modes defined and selected in interfaces outside of the spectrographs. – Modular design compatible with a minimal baseline that can be subsequently expanded and upgraded.
High resolution spectroscopy has been considered of a primary importance to exploit the main scientific cases foreseen for ESO ELT, the Extremely Large Telescope, the future largest optical-infrared telescope in the world. In this context ESO commissioned a Phase-A feasibility study for the construction of a high resolution spectrograph for the ELT, tentatively named HIRES. The study, which lasted 1.5 years, started on March 2016 and was completed with a review phase held at Garching ESO headquarters with the aim to assess the scientific and technical feasibility of the proposed instrument. One of the main tasks of the study is the architectural design of the software covering all the aspects relevant to control an astronomical instrument: from observation preparation through instrument hardware and detectors control till data reduction and analysis. In this paper we present the outcome of the Phase-A study for the proposed HIRES software design highlighting its peculiarities, critical areas and performance aspects for the whole data flow. The End-toEnd simulator, a tool already capable of simulating HIRES end products and currently being used to drive some design decision, is also shortly described.
We present the results from the phase A study of ELT-HIRES, an optical-infrared High Resolution Spectrograph for ELT, which has just been completed by a consortium of 30 institutes from 12 countries forming a team of about 200 scientists and engineers. The top science cases of ELT-HIRES will be the detection of life signatures from exoplanet atmospheres, tests on the stability of Nature’s fundamental couplings, the direct detection of the cosmic acceleration. However, the science requirements of these science cases enable many other groundbreaking science cases. The baseline design, which allows to fulfil the top science cases, consists in a modular fiber- fed cross-dispersed echelle spectrograph with two ultra-stable spectral arms providing a simultaneous spectral range of 0.4-1.8 μm at a spectral resolution of ~100,000. The fiber-feeding allows ELT-HIRES to have several, interchangeable observing modes including a SCAO module and a small diffraction-limited IFU.
The first generation of E-ELT instruments will include an optic-infrared High Resolution Spectrograph, conventionally indicated as EELT-HIRES, which will be capable of providing unique breakthroughs in the fields of exoplanets, star and planet formation, physics and evolution of stars and galaxies, cosmology and fundamental physics. A 2-year long phase A study for EELT-HIRES has just started and will be performed by a consortium composed of institutes and organisations from Brazil, Chile, Denmark, France, Germany, Italy, Poland, Portugal, Spain, Sweden, Switzerland and United Kingdom. In this paper we describe the science goals and the preliminary technical concept for EELT-HIRES which will be developed during the phase A, as well as its planned development and consortium organisation during the study.
The current E-ELT instrumentation plan foresees a High Resolution Spectrograph conventionally indicated as EELTHIRES whose Phase A study has started in March 2016. Since 2013 however, a preliminary study of a modular E-ELT instrument able to provide high-resolution spectroscopy (R~100,000) in a wide wavelength range (0.37-2.5 μm) has been already conducted by an international consortium (termed “HIRES initiative”). Taking into account the requirements inferred from this preliminary work in terms of both high-level operations as well as low-level control, we will present in this paper possible solutions for HIRES hardware and software architecture. The validity of the proposed architectural and hardware choices will be eventually discussed based also on the experience gained on a real-working instrument, ESPRESSO, the next generation high-stability spectrograph for the VLT and to certain extent the precursor of HIRES.
The current E-ELT instrumentation plan foresees a High Resolution Spectrograph conventionally indicated as HIRES whose Phase A study has started in 2016. An international consortium (stemmed from the existing "HIRES initiative") is conducting a preliminary study of a modular E-ELT instrument able to provide highresolution spectroscopy (R ~ 100; 000) in a wide wavelength range (0.37-2.5 μm). For the aims of data treatment (which encompasses both the reduction and the analysis procedures) an end-to-end approach has been adopted, to directly extract scientific information from the observations with a coherent set of interactive, properly validated software modules. This approach is favoured by the specific science objectives of the instrument, which pose unprecedented requirements in terms of measurement precision and accuracy. In this paper we present the architecture envisioned for the HIRES science software, building on the lessons learned in the development of the data analysis software for the ESPRESSO ultra-stable spectrograph for the VLT.
The current instrumentation plan for the E-ELT foresees a High Resolution Spectrograph conventionally indicated as
HIRES. Shaped on the study of extra-solar planet atmospheres, Pop-III stars and fundamental physical constants, HIRES
is intended to embed observing modes at high-resolution (up to R=150000) and large spectral range (from the blue limit to the K band) useful for a large suite of science cases that can exclusively be tackled by the E-ELT. We present in this
paper the solution for HIRES envisaged by the "HIRES initiative", the international collaboration established in 2013 to
pursue a HIRES on E-ELT.
Unveiling the structure of the Broad Line Region (BLR) of AGNs is critical to understand the quasar phenomenon.
Resolving a few BLRs by optical interferometry will bring decisive information to confront, complement and calibrate
the reverberation mapping technique, seed of the mass-luminosity relation in quasars. BLRs are much smaller than the
angular resolution of the VLT and Keck interferometers and they can be resolved only by differential interferometry
very accurate measurements of differential visibility and phase. The latest yields the photocenter variation with λ, and constrains the size, position and velocity law of various regions of the BLR. AGNs are below the magnitude limit for
spectrally resolved interferometry set by currently available fringe trackers. A new “blind” observation method and a
data processing based on the accumulation of 2D Fourier power and cross spectra permitted us the first spectrally
resolved interferometric observation of a BLR, on the K=10 quasar 3C273. A careful bias analysis is still in progress, but
we report strong evidence that, as the baseline increases, the differential visibility decreases in the Paα line. Combined
with a differential phase certainly smaller than 3°, this yields an angular radius of the BLR larger than 0.4
milliarcseconds, or 1000 light days at the distance of 3C273, much larger than the reverberation mapping radius of 300
light days. Explaining the coexistence of these two different scales, and possibly structures and mechanisms, implies
very new insights about the BLR of 3C273.
The convergence of photonics and microelectronics within a single chip is still lacking of a monolithical on-chip optical
amplifier. Rare-earth doped slot waveguides show a large potential as on-chip source. Slot waveguides with silicon
nanocrystals embedded in a dielectric host matrix can increase the light confinement in the active layer and allow
electrical injection. In this work, horizontal slot waveguides formed by two thick silicon layers separated by a thin
erbium doped silicon rich silicon oxide layer are studied as on-chip optical amplifiers. The waveguides are grown in a
CMOS line with the active material grown by low-pressure chemical vapor deposition. Optical tests are performed and
light propagation in the slot waveguides is observed. Using the cut-back technique, spectra propagation losses are
evaluated. Room temperature electroluminescence is observed at 1.54 μm. Transmitted optical signal resonant with Er
absorption is studied as a function of the injected current for different probing laser wavelengths.
Materials used as luminescent down shifters (LDS) have to absorb light effectively in the spectral area where solar cells
have poor internal quantum efficiency. At the same time these materials have to emit most of the absorbed spectral
powers at lower energies where the internal quantum efficiency of the solar cell is close to the maximum. The effects of
silicon nanocrystals prepared by thermal treatment of a silicon-rich-oxide (SRO) layer on the efficiency of c-Si cells are
investigated in this paper. The SRO layer is characterized by a high photoluminescence peak at around 800 nm.
Influence of the active layer on light transmission and on the modification of the optical spectra due to
photoluminescence generation has been determined with the help of optical measurements and transfer matrix
simulations. The solar cell efficiency for cells with and without down-shifting layer were measured under illumination
with AM1.5G solar spectrum and compared with the simulations. Finally, we model the behavior of cells with and
without LDS layer showing that a cell with LDS suffers less from bad surface passivation.
We present the work developed within the science team of the Very Large Telescope Interferometer Spectro-Imager (VSI) during the Phase A studies. VSI aims at delivering ~ 1 milliarcsecond resolution data cubes
in the near-infrared, with several spectral resolutions up to 12 000, by combining up to 8 VLTI telescopes. In
the design of an instrument, the science case plays a central role by supporting the instrument construction
decision, defining the top-level requirements and balancing design options. The overall science philosophy of
VSI was that of a general user instrument serving a broad community. The science team addressed themes
which included several areas of astrophysics and illustrated specific modes of operation of the instrument: a)
YSO disks and winds; b) Multiplicity of young stars; c) Exoplanets; d) Debris disks; e) Stellar surface imaging;
f) The environments of evolved stars; g) AGN tori; h) AGN's Broad Line Region; i) Supermassive black-holes;
and j) Microlensing. The main conclusions can be summarized as follows: a) The accessible targets and related
science are extremely sensitive to the instrument limiting magnitude; the instrument should be optimized for
sensitivity and have its own fringe tracker. b) Most of the science cases are readily achievable with on-axis fringe
tracking, off-axis fringe tracking enabling extra science. c) In most targets (YSOs, evolved stars and AGNs), the
interpretation and analysis of circumstellar/nuclear dust morphology requires direct access to the gas via spectral
resolved studies of emission lines, requiring at least a spectral resolution of 2 500. d) To routinely deliver images
at the required sensitivity, the number of telescopes in determinant, with 6 telescopes being favored. e) The
factorial increase in the number of closure phases and visibilities, gained in a single observation, makes massive
surveys of parameters and related science for the first time possible. f) High dynamic range imaging and very
high dynamic range differential closure phase are possible allowing the study of debris disks and characterization
of pegasides. g) Spectro-imaging in the near-infrared is highly complementary to ALMA, adaptive optics and
interferometric imaging in the thermal infrared.
KEYWORDS: Telescopes, Stars, Spectral resolution, Spatial resolution, Interferometry, Integrated optics, Space telescopes, Visibility, Image restoration, Signal to noise ratio
The VLTI Spectro Imager (VSI) was proposed as a second-generation instrument of the Very Large Telescope Interferometer
providing the ESO community with spectrally-resolved, near-infrared images at angular resolutions
down to 1.1 milliarcsecond and spectral resolutions up to R = 12000. Targets as faint as K = 13 will be imaged
without requiring a brighter nearby reference object; fainter targets can be accessed if a suitable reference is
available. The unique combination of high-dynamic-range imaging at high angular resolution and high spectral
resolution enables a scientific program which serves a broad user community and at the same time provides the
opportunity for breakthroughs in many areas of astrophysics. The high level specifications of the instrument are
derived from a detailed science case based on the capability to obtain, for the first time, milliarcsecond-resolution
images of a wide range of targets including: probing the initial conditions for planet formation in the AU-scale
environments of young stars; imaging convective cells and other phenomena on the surfaces of stars; mapping
the chemical and physical environments of evolved stars, stellar remnants, and stellar winds; and disentangling the central regions of active galactic nuclei and supermassive black holes. VSI will provide these new capabilities
using technologies which have been extensively tested in the past and VSI requires little in terms of new
infrastructure on the VLTI. At the same time, VSI will be able to make maximum use of new infrastructure as it
becomes available; for example, by combining 4, 6 and eventually 8 telescopes, enabling rapid imaging through
the measurement of up to 28 visibilities in every wavelength channel within a few minutes. The current studies
are focused on a 4-telescope version with an upgrade to a 6-telescope one. The instrument contains its own
fringe tracker and tip-tilt control in order to reduce the constraints on the VLTI infrastructure and maximize
the scientific return.
We present interferometric near-infrared observations of the Luminous Blue Variable (LBV) η Car using the
Very Large Telescope Interferometer (VLTI) and the AMBER instrument of the European Southern Observatory
(ESO). A high spatial resolution of 5 mas (~11.5 AU) and a high spectral resolution R = λ/Δλ=1500 and
12000 were obtained. Some of the data was recorded using the fringe tracker FINITO. The observations were
obtained in the wavelength range around both the He I 2.059 μm and the Brγ 2.166 μm emission lines. The
AMBER interferograms allow the investigation of the wavelength dependence of η Car's visibility, wavelength-differential phase, and closure phase. If we fit Hillier et al. model visibilities to the observations, we obtain
50% encircled-energy diameters of 4.2, 6.5 and 9.6 mas in the 2.17 μm continuum, the He I, and the Brγ emission
lines, respectively. In the continuum, an elongation along a position angle of 120° ± 15° was derived from the
visibilities. The VLTI observations support theoretical models of anisotropic winds from fast-rotating, luminous
hot stars with enhanced high-velocity mass loss near the pole.
We present the first interferometric NIR observations of the LBV η Carinae with high spectral resolution. The observations were carried out with three 8.2 m VLTI Unit Telescopes in the K-band. The raw data are spectrally dispersed interferograms obtained with spectral resolutions of 1,500 (MR-K mode) and 12,000 (HR-K mode). The observations were performed in the wavelength range around both the He I 2.059 μm and the Brγ 2.166 μm emission lines. The spectrally dispersed AMBER interferograms allow the investigation of the wavelength dependence of the visibility, differential phase, and closure phase of η Car. In the K-band continuum, a diameter of 4.0±0.2 mas (Gaussian FWHM) was measured for η Car's optically thick wind region, whereas the Brγ and He I emission line regions are larger. If we fit Hillier et al. model visibilities to the observed AMBER visibilities, we obtain 50% encircled-energy diameters of 4.3, 6.5 and 9.6 mas in the 2.17 μm continuum, the He I, and the Brγemission lines, respectively. In the continuum near the Brγ line, an elongation along a position angle of 128° ± 15° was found, consistent with previous VLTI/VINCI measurements. We find good agreement between the measured visibilities and the predictions of the radiative transfer model of Hillier et al. For the interpretation of the non-zero differential and closure phases measured within the Brγ line, we present a simple geometric model of an inclined, latitude-dependent wind zone. Our observations support theoretical models of anisotropic winds from fast-rotating, luminous hot stars with enhanced high-velocity mass loss near the polar regions.
AMBER had first light in March 2004. The guaranteed time observations of the AMBER consortium (LAOG, MPIfR, OAA, OCA, UNSA) consists of 87 proposals ranging from cosmology, extragalactic studies, star formation, planetary system, late stages of stellar evolution to physical properties of stars. Some examples, AGN, evolved stars and hot stars are discussed in this paper.
AMBER is the near-infrared instrument of the Very Large Telescope Interferometer (VLTI). With a spectral resolution up to 10000 in the
1.2-2.4 micron wavelength range, AMBER will offer the possibility to
combine 3 beams from the VLTI array either 8-m or 1.8m telescopes. The instrument has been designed to bring high precision measurement and high sensitivity and therefore opens the way to new domain of investigation in stellar physics and for the first time access to extragalactic sources. We show how the performance of the instrument can apply in these different astrophysical fields. We present the work of the Science Group and the AMBER consortium who defined precise astrophysical goals for the first years of operation.
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