共查询到20条相似文献，搜索用时 640 毫秒
1.
2.
Andreas Eckart 《Astronomische Nachrichten》2005,326(7):559-573
E01 VLTI‐PRIMA Fringe Tracking Testbed E02 The Fringe and Flexure Tracking System for the LBT interferometric camera LINC‐NIRVANA E03 GRAVITY: The AO assisted, two object beam combiner instrument for the VLTI E04 (Re)Solving the dynamic atmospheres of carbon‐rich giants E05 Do's and Don'ts of MIDI Data‐reduction E06 Bispectrum speckle imaging of the ultracompact HII region K3‐50A E07 Differential astrometry and astrometric planet searches with the VLTI E08 First AU‐scale observations of V1647 Ori: The outbursting young star in the McNeil's Nebula E09 Mid‐infrared imaging at the VLTI: An APreS‐MIDI image reconstruction study E10 VLTI/MIDI observation of the silicate carbon star Hen 38 (IRAS08002‐3803): Silicate dust reservoir spatially resolved for the first time E11 Mid‐infrared spectro‐interferometric observation of the Mira variable RR Sco with the VLTI/MIDI instrument E12 Scientific Prospects for VLTI in the Galactic Centre: Getting to the Schwarzschild Radius E13 VLTI near‐infrared observations of the stellar multiple system δ Velorum E14 The first VLTI observations of the Galactic Center E15 Bispectrum speckle interferometry of the massive protostellar outflow source IRAS 23151+5912 E16 Interferometric Observations of Infrared Companions with MIDI E17 Evolution and radial distribution of dust in the inner 1‐10A.U. of circumstellar disks around low‐mass young stellar objects. E18 Near‐infrared Interferometry with the AMBER Instrument of the VLTI E19 APreS‐MIDI ‐ Interferometic Imaging in the Mid‐Infrared E20 Mining the sky: Selection of extragalactic targets for interferometric observations 相似文献
3.
Radiative Transfer (RT) codes with image capability are a fundamental tool for preparing interferometric observations and
for interpreting visibility data. In view of the upcoming VLTI facilities, we present the first comparison of images/visibilities
coming from two 3D codes that use completely different techniques to solve the problem of self-consistent continuum RT. In
addition, we focus on the astrophysical case of a disk distorted by tidal interaction with by-passing stars or internal planets
and investigate for which parameters the distortion can be best detected in the mid-infrared using the mid-infrared interferometric
device MIDI.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
4.
A. Eckart T. Bertram N. Mouawad T. Viehmann C. Straubmeier J. Zuther 《Astrophysics and Space Science》2003,286(1-2):269-276
VLTI interferometry will allow imaging of galactic and extragalactic sources with milliarcsecond angular resolution. For moderately
bright sources the spectral resolution will be of the order of 10000. These capabilities will allow detailed studies of solar
system objects, stars, proto-planetary systems and the detection of hot extra-solar planets. The observations of galactic
nuclei will allow unprecedented measurements of physical parameters in these systems. VLTI will be a prime instrument to study
the immediate environment of the massive black hole at the center of the Milky Way. With the exception of a few `self-referencing'
sources the observations of extragalactic nuclei will benefit from an extended capability for simultaneous measurements of
nearby reference sources for fringe tracking. With beam combination instruments like AMBER, MIDI, PRIMA, and GENIE the VLTI
will reach full maturity at a time when other interferometric instruments at different wavelengths will be fully operational.
Most important are ALMA (in the mm- and sub-mm-domain), LOFAR and SKA (in the radio meter to centimeter domain) and of course
VLB-networks in the radio, and other – at that time –well developed interferometers in the optical. A major scientific potential
of future scientific VLTI programs will lie in an efficient combination of these high angular resolution capabilities.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
Margarita Karovska Martin Elvis Massimo Marengo 《Astrophysics and Space Science》2003,286(1-2):261-266
We present here a new method using interferometric measurements of quasars, that allows the determination of direct geometrical
distances on cosmic scales. Quasar Broad Emission Line Regions sizes provide a `meter rule' with which to measure the metric
of the Universe. This method is less dependent of model assumptions, and even of variations in the fundamental constants (other
than c).We discuss the spectral and spatial requirements on the VLTI observations needed to carry out these measurements.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
6.
Ch. Leinert U. Graser F. Przygodda L.B.F.M. Waters G. Perrin W. Jaffe B. Lopez E.J. Bakker A. Böhm O. Chesneau W.D. Cotton S. Damstra J. de Jong A.W. Glazenborg-Kluttig B. Grimm H. Hanenburg W. Laun R. Lenzen S. Ligori R.J. Mathar J. Meisner S. Morel W. Morr U. Neumann J.-W. Pel P. Schuller R.-R. Rohloff B. Stecklum C. Storz O. von der Lühe K. Wagner 《Astrophysics and Space Science》2003,286(1-2):73-83
After more than five years of preparation, the mid-infrared interferometric instrument MIDI has been transported to Paranal
where it will undergo testing and commissioning on theVery Large Telescope Interferometer VLTI from the end of 2002through
large part of this year 2003. Thereafter it will be available as a user instrument to perform interferometric observations
over the8 μm–13 μm wavelength range, with a spatial resolution of typically 20 milliarcsec, a spectral resolution of up to
250, and an anticipated point source sensitivity of N = 3–4 mag or 1–2.5 Jy for self –fringe tracking, which will be the only
observing mode during the first months of operation. We describe the layout of the instrument, laboratory tests, and expected
performance, both for broadband and spectrally resolved observing modes. We also briefly outline the planned guaranteed time
observations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
7.
Marco Delbo Mario Gai Sebastiano Ligori Laura Saba Davide Gandolfi Carlo Blanco Markus Wittkowski 《Icarus》2006,181(2):618-622
The Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO) can be used to obtain direct determination of the sizes and the albedos of asteroids. We present results of the first attempt to carry out interferometric observations of asteroids with the Mid Infrared Interferometric Instrument (MIDI) at the VLTI. Our target was 1459 Magnya. This is the only V-type asteroid known to exist in the outer main-belt, and its IRAS-albedo turns out to be rather low for an object of this taxonomic class. Interferometric fringes were not detected, very likely due to the fact that the flux emitted by the asteroid was lower than expected and below the MIDI threshold for fringe detection. However, by fitting the Standard Thermal Model to the N-band infrared flux measured by MIDI in photometric mode and to the visible absolute magnitude, obtained from quasi-simultaneous B- and V-band photometric observations, we have derived a geometric visible albedo of 0.37±0.06 and an effective diameter of 17±1 km. This new estimate of the albedo differs from that previously obtained by IRAS and is more consistent with the V-type taxonomic classification of 1459 Magnya. 相似文献
8.
Joel Sanchez-Bermudez Florentin Millour Fabien Baron Roy van Boekel Laurent Bourgès Gilles Duvert Paulo J. V. Garcia Nuno Gomes Karl-Heinz Hofmann Thomas Henning Jacob W. Isbell Bruno Lopez Alexis Matter J-Uwe Pott Dieter Schertl Eric Thiébaut Gerd Weigelt John Young 《Experimental Astronomy》2018,46(3):457-473
During the last two decades, the first generation of beam combiners at the Very Large Telescope Interferometer has proved the importance of optical interferometry for high-angular resolution astrophysical studies in the near- and mid-infrared. With the advent of 4-beam combiners at the VLTI, the u ? v coverage per pointing increases significantly, providing an opportunity to use reconstructed images as powerful scientific tools. Therefore, interferometric imaging is already a key feature of the new generation of VLTI instruments, as well as for other interferometric facilities like CHARA and JWST. It is thus imperative to account for the current image reconstruction capabilities and their expected evolutions in the coming years. Here, we present a general overview of the current situation of optical interferometric image reconstruction with a focus on new wavelength-dependent information, highlighting its main advantages and limitations. As an Appendix we include several cookbooks describing the usage and installation of several state-of-the art image reconstruction packages. To illustrate the current capabilities of the software available to the community, we recovered chromatic images, from simulated MATISSE data, using the MCMC software SQUEEZE. With these images, we aim at showing the importance of selecting good regularization functions and their impact on the reconstruction. 相似文献
9.
K. J. Johnston J. H. Spencer G. H. Kaplan W. J. Klepczynski D. D. McCarthy 《Celestial Mechanics and Dynamical Astronomy》1980,22(2):143-151
A review of the accuracy of radio interferometric positions of extragalactic sources is given. A mean catalog of radio positions is presented. With the accuracy currently attainable, radio observations can contribute significantly to the determination of astronomical constants. 相似文献
10.
Klaus Maisinger M. P. Hobson Richard D. E. Saunders Keith J. B. Grainge 《Monthly notices of the Royal Astronomical Society》2003,345(3):800-808
Interferometers require accurate determination of the array configuration in order to produce reliable observations. A method is presented for finding the maximum-likelihood estimate of the telescope geometry, and of other instrumental parameters, astrometrically from the visibility timelines obtained from observations of celestial calibrator sources. The method copes systematically with complicated and unconventional antenna and array geometries, with electronic bandpasses that are different for each antenna radiometer, and with low signal-to-noise ratios for the calibrators. The technique automatically focuses on the geometry errors that are most significant for astronomical observation. We apply this method to observations made with the Very Small Array and constrain some 450 telescope parameters, such as the antenna positions, effective observing frequencies and correlator amplitudes and phaseshifts; this requires only ∼1 h of CPU time on a typical workstation. 相似文献
11.
D. Defrère O. Absil J.-P. Berger T. Boulet W. C. Danchi S. Ertel A. Gallenne F. Hénault P. Hinz E. Huby M. Ireland S. Kraus L. Labadie J.-B. Le Bouquin G. Martin A. Matter A. Mérand B. Mennesson S. Minardi J. D. Monnier B. Norris G. Orban de Xivry E. Pedretti J.-U. Pott M. Reggiani E. Serabyn J. Surdej K. R. W. Tristram J. Woillez 《Experimental Astronomy》2018,46(3):475-495
The development of high-contrast capabilities has long been recognized as one of the top priorities for the VLTI. As of today, the VLTI routinely achieves contrasts of a few 10??3 in the near-infrared with PIONIER (H band) and GRAVITY (K band). Nulling interferometers in the northern hemisphere and non-redundant aperture masking experiments have, however, demonstrated that contrasts of at least a few 10??4 are within reach using specific beam combination and data acquisition techniques. In this paper, we explore the possibility to reach similar or higher contrasts on the VLTI. After reviewing the state-of-the-art in high-contrast infrared interferometry, we discuss key features that made the success of other high-contrast interferometric instruments (e.g., integrated optics, nulling, closure phase, and statistical data reduction) and address possible avenues to improve the contrast of the VLTI by at least one order of magnitude. In particular, we discuss the possibility to use integrated optics, proven in the near-infrared, in the thermal near-infrared (L and M bands, 3-5 \(\upmu \)m), a sweet spot to image and characterize young extra-solar planetary systems. Finally, we address the science cases of a high-contrast VLTI imaging instrument and focus particularly on exoplanet science (young exoplanets, planet formation, and exozodiacal disks), stellar physics (fundamental parameters and multiplicity), and extragalactic astrophysics (active galactic nuclei and fundamental constants). Synergies and scientific preparation for other potential future instruments such as the Planet Formation Imager are also briefly discussed. This project is called Hi-5 for High-contrast Interferometry up to 5 μm. 相似文献
12.
A. Quirrenbach 《Astrophysics and Space Science》2003,286(1-2):277-289
The scientific capabilities of the VLT Interferometer can be substantially enhanced through new focal-plane instruments. Many
interferometric techniques– astrometry, phase-referenced imaging, nulling, and differential phase measurements – require control
of the phase to ≲ 1 rad; this capability will be provided at the VLTI by the PRIMA facility. Phase-coherent operation of the
VLTI will also make it possible to perform interferometry with spectral resolution up to R ∼ 100,000 by building fiber links
to the high-resolution spectrographs UVES and CRIRES. These developments will open new approaches to fundamental problems
in fields as diverse as extra solar planets,stellar atmospheres, circumstellar matter, and active galactic nuclei.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
This practice work session introduces the participants to the ESO tools available for the reduction of VLTI/AMBER data. They include Gasgano and Reflex. These tools are provided by ESO, and are based on amdlib, provided by the AMBER consortium. 相似文献
14.
M. Marengo M. Karovska D.D. Sasselov C. Papaliolios J.T. Armstrong T.E. Nordgren 《Astrophysics and Space Science》2003,286(1-2):185-190
We present a new method to compute wavelength- and phase-dependent limb darkening corrections for classical Cepheids. These
corrections are derived from hydrodynamic simulations and radiative transfer modeling with a full set of atomic and molecular
opacities. Comparison with hydrostatic models having the same stellar parameters show a larger limb darkening for most phases
in our models, and temporal variations related to the hydrodynamics of the stellar pulsation. Weassess the implications of
our results with respect to the geometric Baade-Wesselink method, which uses interferometric measurements of Cepheid angular
diameters to determine their distances and radii. The relevance of the hydrodynamic effects predicted by our model on the
limb darkening of pulsating Cepheids is finally discussed in terms of the predicted capabilities of the VLTI.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
15.
We present first observations of Mira stars obtained at the Very Large Telescope Interferometer (VLTI) at 2 microns, equipped
with the VINCI instrument, using different baselines with both the test siderostats and the 8.2 m unit telescopes. These observations,
collected in the course of the VLTI commissining program, have targeted so far about sixty cool giant stars. In this talk,
we list and describe the measurements obtained for 14 Mira stars, many of them representing first-time determinations of the
visibility. In particular, we devote special attention to a study of Mira itself, for which very accurate determinations of
the visibility at several baseline lenghts and orientations could be obtained. We find that a two-component model is more
consistent with the data than a single stellar disc. Further observations are needed for a better understanding of this source.
The VLTI will constitute an ideal instrument for such studies in the future. In particular it will permit detailed investigations
of southern AGB stars, such as accurate measurements of surface structureparameters (diameters, diameter variations, asymmetries,
center-to-limbvariations, special features like hot spots) and of circumstellar envelopes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
17.
J.A. Meisner 《Astrophysics and Space Science》2003,286(1-2):119-127
Although primarily intended as a test and alignment instrument in order to commission the VLTI, VINCI has taken useful scientific
data in its first year and a half of operation. Our results employ coherent integration of fringe visibility in which the
actual amplitudes of the raw scans are combined linearly after correcting for the position of the fringe within each scan.
In addition to reducing the effect of noise compared to incoherent integration, the result contains a broader range of information,
including an estimate of the complex visibility spectrum. Such an estimator is thus sensitive to instrumental phase and spectral
characteristics, including the variable component of dispersion introduced by the excess air paths in the delay lines. Calibration
of such instrumental effects demonstrates the ability to detect source phase at a fine level as will be required for direct
interferometric detection of extra solar planets. We present diameters for five stars obtained by observing the visibility
null in their correlated spectra. Using coherent integration we have also observed the peculiar correlated spectra seen in
many Mira variables, possibly due to changes in the apparent diameter with wavelength. Calibration of the zero-baseline power
from o Ceti is used with other interferometric observations of this star over a period of 90 days to plot diameter variations associated
with its pulsation cycle.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
18.
Guy Perrin 《Astrophysics and Space Science》2003,286(1-2):197-212
Late-type giant stars have been traditional targets for infrared interferometers. They are bright and big and are therefore
easy targets to resolve and to detect. Considerable progress has been and is being made on the spatial structure of these
objects thanks to existing interferometers. Beyond the classical measurement of their diameters, pulsations have been directly
detected, spatial intensity distributions are more and more understood and more important, consistent scenarios for both spectroscopic
and interferometric measurements are on the verge to be validated. All this has been possible with prototype instruments having
a small number of baselines and very limited spectral capabilities. AMBER and MIDI will surely open a new era with high spectral
resolution, high efficiency and imaging capabilities. This is not an exhaustive review of all the work done in the field but
rather a presentation of the context. A recent review of Mira star observations with interferometers was recently written
(Scholz, 2003).A brief science case is first introduced in this paper. Achievements with high angular resolution single-telescope
techniques are presented. The contributions of optical and infrared interferometers are then explained. Eventually, some hints
about the possible progress with VLTI are discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Frank Przygodda O. Chesneau U. Graser Ch. Leinert S. Morel 《Astrophysics and Space Science》2003,286(1-2):85-91
MIDI, the MID-Infrared Interferometricnterferometric Instrument for ESO's Very Large Telescope Interferometer (VLTI), will be the first instrument for combining
mid-infrared light directly in order to obtain angular resolution up to 10 mas (assuming a 200 m baseline) in a wavelength
range from 8 to 13 μm. Currently in the phase of commissioning at Paranal, the start of its scientific operation is expected
for summer 2003. Direct interferometry at thermal infrared wavelengths demands special requirements on the instrument and
also on the procedures of preparation of data reduction. Hereafter MIDI's different observing modes are described and an example
for an interferometric observation is given.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
20.
Toshio Fukushima Masa-Katsu Fujimoto Hiroshi Kinoshita Shinko Aoki 《Celestial Mechanics and Dynamical Astronomy》1986,38(3):215-230
The relation between the units and readings of time and space coordinates of terrestrial and barycentric reference frames is discussed from the viewpoint of general relativity. Attention is paid to the unit of space coordinates since the International Astronomical Union (IAU) regulates only the unit of time in the above two frames. Two definitions of unit of length are examined and their effects on the numerical expression of coordinate transformation, equations of planetary motions, and those for light propagation time are discussed. A clear conflict is found between the IAU (1976) recommendation on the definition of the time-scales in different frames of reference and the statement that all constants in the IAU (1976) new system of astronomical constants are defined in terms of the Internationsl System of units (SI units). One of the above two definitions is proposed to resolve this conflict by the least alteration to current procedures for analysing the recent astrometric observations such as the radar/laser rangings, the range and range-rate, and the very long baseline interferometric observations. Also, an interpretation of numerical values in the IAU (1976) new system of astronomical constants is presented. It is stressed that the definition proposed in this paper requires that a formula slightly different from that in current use be employed in the numerical transformation of readings of coordinates between the terrestrial and barycentric reference frames. 相似文献