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1.
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
2.
This chapter gives some indications on the selection of suitable astronomical calibrators for interferometric observations. After an introduction to interferometric calibrations, we will focus on the criteria, steps and tools developed by ESO to prepare VLTI observations and to select calibrators. Although the tools described here are focused on VLTI, the problem of astronomical calibrators is the same for the other interferometers and can be approached in the same way. 相似文献
3.
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
4.
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
5.
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
6.
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
7.
ESO intends to actively and vigorously support the search for extrasolar planets by designing and commissioning instruments and methods targeted towards this end. High precision radial velocity measurements at La Silla and Paranal, wide-field microlensing imaging in the bulge from Paranal, and very high spatial resolution observations with the VLT Interferometer are but a few of the exciting new techniques ESO plans to bring on line in the next few years. I will discuss in detail the expected or actual performance of each of these methods and review the scientific potential for progress in the field of extrasolar planet research that they are expected to bring. 相似文献
8.
Simon Albrecht Andreas Quirrenbach Robert N. Tubbs Ramon Vink 《Experimental Astronomy》2010,27(3):157-186
The combination of high spatial and spectral resolution in optical astronomy enables new observational approaches to many
open problems in stellar and circumstellar astrophysics. However, constructing a high-resolution spectrograph for an interferometer
is a costly and time-intensive undertaking. Our aim is to show that, by coupling existing high-resolution spectrographs to
existing interferometers, one could observe in the domain of high spectral and spatial resolution, and avoid the construction
of a new complex and expensive instrument. We investigate in this article the different challenges which arise from combining
an interferometer with a high-resolution spectrograph. The requirements for the different sub-systems are determined, with
special attention given to the problems of fringe tracking and dispersion. A concept study for the combination of the VLTI
(Very Large Telescope Interferometer) with UVES (UV-Visual Echelle Spectrograph) is carried out, and several other specific
instrument pairings are discussed. We show that the proposed combination of an interferometer with a high-resolution spectrograph
is indeed feasible with current technology, for a fraction of the cost of building a whole new spectrograph. The impact on
the existing instruments and their ongoing programs would be minimal. 相似文献
9.
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
10.
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
11.
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
12.
C. Denker 《Astronomische Nachrichten》2010,331(6):648-651
The next generation of solar telescopes will enable us to resolve the fundamental scales of the solar atmosphere, i.e., the pressure scale height and the photon mean free path. High‐resolution observations of small‐scale structures with sizes down to 50 km require complex post‐focus instruments, which employ adaptive optics (AO) and benefit from advanced image restoration techniques. The GREGOR Fabry‐Pérot Interferometer (GFPI) will serve as an example of such an instrument to illustrate the challenges that are to be expected in instrumentation and data analysis with the next generation of solar telescopes (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
AMBER is the General User near infrared focal instrument of the Very Large Telescope Interferometer. It is a single mode,
dispersed fringes, three telescope instrument. A limiting magnitude of the order of H=13 will allow tackling of a fair sample
of extra galactic targets. A very high accuracy, in particular in color differential phase and closure phase modes gives good
hope for very high dynamical range observations, possibly including hot extra solar planets. The relatively high maximum spectral
resolution, up to 10000, will allow stellar activity observations. Between these extreme goals, AMBER has a wide range of
applications including Young Stellar Objects, Evolved Stars, circumstellar material and many others.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
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
15.
A. Glindemann J. Algomedo R. Amestica P. Ballester B. Bauvir E. Bugueño S. Correia F. Delgado F. Delplancke F. Derie Ph. Duhoux E. di Folco A. Gennai B. Gilli P. Giordano Ph. Gitton S. Guisard N. Housen A. Huxley P. Kervella M. Kiekebusch B. Koehler S. Lévêque A. Longinotti S. Ménardi S. Morel F. Paresce T. Phan Duc A. Richichi M. Schöller M. Tarenghi A. Wallander M. Wittkowski R. Wilhelm 《Astrophysics and Space Science》2003,286(1-2):35-44
The Very Large Telescope (VLT) Observatory on Cerro Paranal (2635 m) in Northern Chile is approaching completion. After the
four 8-m Unit Telescopes (UT) individually saw first light in the last years, two of them were combined for the first time
on October 30, 2001 to form a stellar interferometer, the VLT Interferometer. The combination in pairs of all four UTs was
completed in September 2002. In this article, we will describe the subsystems of the VLTI and the planning for the following
years.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Samuel Lévêque Bertrand Koehler Oskar von der Lühe 《Astrophysics and Space Science》1996,239(2):305-314
The Very Large Telescope Interferometer [1,13] will be operated in air which will introduce small optical path fluctuations due to internal turbulence [4,6] and dispersion effects. Both may contribute to fringe contrast decrease. Longitudinal dispersion effects can be corrected by inserting an appropriate glass of variable thickness in one arm of the interferometer [3,5,11,12]. This paper presents a new method applied to VLTI in order to select the optimum glass, according to both the observing wavelength and the spectral bandpath, and to calculate its thickness. Results are presented in terms of improvement on the fringe contrast. 相似文献
17.
由于地球电离层的阻挡以及其他干扰,在地面难以进行有效的甚低频天文观测,而使用搭载于绕地或绕月轨道卫星上的甚低频天线进行干涉观测会大大提高观测灵敏度和角分辨率.卫星定位精度会影响观测数据的处理结果,进而影响成图质量,并且会大幅影响飞行项目的复杂度和总成本.首先分析卫星姿态控制精度和星间基线测量精度对绕地轨道甚低频干涉观测的影响,之后对干涉观测中信号延时误差进行仿真,研究延时误差与数据相关处理中条纹搜索范围之间的关系,并对数据计算速度需求进行估算.分析和仿真结果可以辅助相关空间甚低频观测项目总体方案的制定和工程指标的优化. 相似文献
18.
Albert Van Helden 《Experimental Astronomy》2009,25(1-3):3-16
The first century of telescopic astronomy can be divided into two periods. During the first, from 1609 to ca. 1640, observations were made with a simple “Dutch” or “Galilean” telescope with a concave eyepiece. Galileo made all his discoveries with this instrument. Its limited field of view, however, made magnifications of more than about 20 impractical, and therefore this instrument’s limit had been reached within a few years. During the second period, ca. 1640–ca. 1700, the simple astronomical telescope came into use, almost immediately augmented with a field lens and an erector lens (the latter used only for terrestrial purposes). Magnifications were increased by increasing the focal lengths of objectives, and this quickly led to very long telescopes, often used without a tube. The astronomical discoveries made possible by this form of the instrument were, however, made with instruments of relatively modest lengths. By the end of the century, very long telescopes fell out of use, while shorter ones were adapted for measurements. Further discoveries became possible only with the reflecting telescope in the second half of the eighteenth century. 相似文献
19.
F. Malbet 《Astrophysics and Space Science》2003,286(1-2):131-144
The study of Young Stellar Objects (YSOs) is one of the most exciting topics that can be undertaken by long baseline optical
interferometry. The magnitudes of these objects are at the edge of capabilities of current optical interferometers, limiting
the studies to a few dozen, but are well within the capability of coming large aperture interferometers like the VLT Interferometer,
the Keck Interferometer, the Large Binocular Telescope or 'OHANA. The milli-arcsecond spatial resolution reached by interferometry
probes the very close environment of young stars, down to a tenth of an astronomical unit. In this paper, I review the different
aspects of star formation that can be tackled by interferometry: circumstellar disks, multiplicity, jets. I present recent
observations performed with operational infrared interferometers, IOTA, PTI and ISI, and I show why in the next future one
will extend these studies with large aperture interferometers.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献