Interferometry theory primer

As an introduction to the following talks, this presentation reviews the theoretical background of interferometric measurements. Starting from a general formalism, I then emphasize the relationship between those measurements and the observed object properties. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of the hard X-ray imaging experiment timax: Laboratory images and first balloon flight

We present calibration results and laboratory images produced by the balloon-borne hard X-ray imaging telescope TIMAX. The images were produced with an²⁴¹Am radioactive source placed 45 m away from the detector plane, in the center of the field of view. It is shown that the mask 3-antimask imaging reconstruction process, when combined with flat-fielding techniques, is very effective at recovering signal-to-noise ratio lost due to systematic non-uniformity in the background measured by the 35 detectors. The experiment was launched in June 8th, 1993 from Birigüi, SP, Brazil, onboard a 186,000 m³ stratospheric balloon, and remained at an atmospheric depth of 2 g cm^–2su for 8 hours. Even though no scientific data were gathered in this first flight, we obtained valuable engineering data and could also calculate the sensitivity of the experiment based on the instrumental background spectrum at balloon altitudes. In the 60–70 keV energy band, the experiment can detect 3 sources at a level of 1.2 x 10^–4 photons cm^–2 s^–1 keV^–1 for an integration of 6 hours at 2.1 g cm^–2.     

Interferometry with the Large Binocular Telescope

The Large Binocular Telescope (LBT) will be the largest single telescope in the world when it is completed in 2005. The unique structure of the telescope incorporates two, 8.4 meter diameter primary mirrors on a 14.4 meter center-to-center mounting. This configuration provides the equivalent collecting area of a 12 meter telescope, and when combined coherently, the two optical paths offer very interesting possibilities for interferometry. Two initial interferometric instruments are planned for the LBT. A group based at the University of Arizona is constructing LBTI, a pupil-plane, nulling beam combiner operating in the thermal infrared N band. This instrument will search for and measure zodiacal light in candidate stellar systems for the Terrestrial Planet Finder (TPF) and Darwin missions. Expansion ports can accomodate additional instruments. A second group, based in Heidelberg, Arcetri, and Köln, is building LINC-NIRVANA, a near-infrared Fizeau-mode beam combiner. This type of observation preserves phase information and allows true imagery over a wide field of view. Using state-of-the-art detector arrays, coupled with advanced adaptive optics, LINC-NIRVANA will deliver the sensitivity of a 12 m telescope and the spatial resolution of a 23 m telescope, over a field of view up to 2 arc minutes square.     

Development of the HEFT and NuSTAR focusing telescopes

Hard X-ray/soft gamma-ray astrophysics is on the verge of a major advance with the practical realization of technologies capable of efficiently focusing X-rays above 10 keV. Hard X-ray focusing telescopes can achieve orders of magnitude improvements in sensitivity compared to the instruments based on coded apertures and collimated detectors that have traditionally been employed in this energy band. Compact focal planes enable high-performance detectors with good spectral resolution to be employed in efficient, low-background configurations. We have developed multilayer coated grazing incidence optics and solid state Cadmium Zinc Telluride focal plane systems for the High Energy Focusing Telescope (HEFT) balloon-borne experiment, and for the Nuclear Spectroscopic Telescope Array (NuSTAR) Small Explorer satellite. In this paper we describe the technologies, telescope designs, and performance of both experiments.     

The Square Kilometre Array: An International Engineering Perspective

The pace of the international Square Kilometre Array (SKA) project is accelerating, with major concept reviews recently completed and a number of technology demonstrators well underway. First-round submissions to host the telescope were lodged by six countries. The SKA timeline currently shows a site decision in 2006, and one or more technology concepts chosen in 2008. The telescope is expected to be operational, in various phases, in the period 2015–2020. This paper gives a status review of the project, and outlines engineering concept development and demonstration projects.     

Observations of the X-ray binaries 4U 1700-37 and GRO J1655-40 during the Grif experiment onboard the mir orbiting station

Various areas of the sky, including the Galactic-center region and the region with the X-ray binaries 4U 1700-37 and GRO J1655-40, were observed in the hard (10–300 keV) energy range during the Grif experiment onboard the Mir orbiting station. An epoch-folding analysis of the data has revealed periodicities with periods of 82 and 62 h, which are equal to the orbital periods of 4U 1700-37 and GRO J1655-40. Previously, these periodicities were observed during the Prognoz-9 X-ray experiment. Periodicities with periods in the range of days, 98 and 152 h, which were also observed during the Prognoz-9 experiment, were not revealed by the Grif data. We obtained upper limits on the intensities of these periodicities in various energy ranges. For the 62-h periodicity, we constructed an average 25–50-keV light curve and estimated the spectral flux density, which characterizes the intensity of the periodic component at different energies in different observing intervals during 1995–1997. The Prognoz-9 and Grif observations of GRO J1655-40 are compared with its CGRO, RXTE, and BeppoSax observations. The orbital periodicity is shown to manifest itself in the hard emission from the extremely bright X-ray transient GRO J1655-40, a likely black-hole candidate, even at the epochs between its X-ray outbursts.     

三能级Tonks-Girardeau气体的Ramsey干涉的研究

采用Ramsey分离振荡场方法,研究了紧束缚一维强相互作用的超冷玻色气体在Tonks-Girardeau区的Ramsey干涉。在等失谐情况下,干涉条纹宽度随着原子与分离场作用时间和拉比(Rabi)频率的增大而变窄。对量子投影噪声的研究表明,相比二能级Tonks-Girardeau气体,对于三能级模型,通过控制原子总数和调节外场可以降低量子噪声,有效地减少噪声对Tonks-Girardeau气体系统的干扰。原子干涉的探索对提高量子频率标准的精度具有重要理论指导意义。     

连线干涉系统测量共位双星宽带信号处理与分析

随着人类空间活动的急剧增加,同步轨道资源已变得十分稀缺。为此人们采用了多星共位技术,来充分挖掘同步轨道资源。多星共位中,由于卫星存在位置漂移的情况,安全问题成为维护卫星正常工作必须考虑的问题之一。考虑到同步卫星的轨道特性,常采用三程测距的方式对卫星进行测轨,而且需要较长时间的测轨弧段。连线干涉测量可以获得高精度的差分相位时延,这对卫星在垂直视线方向上构成了很强的约束。给出了连线干涉测量系统设计及测量数据处理方法,并对测量中的关键技术与设备特性、测量数据精度进行了初步分析。     

Simulation Research on the Solar Hard X-Ray Imaging Telescope

The hard X-ray imaging telescope of the modulation collimator type is widely used in current solar observations. The spatial modulation telescope is the telescope which keeps its central axis not rotate, suitable for the satellite of 3-axis attitude stabilization. For the possible Chinese solar mission in the near future, we make a design of hard X-ray imaging telescope, and simulate the photon counting using the common simulation software GEANT4. Then we implement the image reconstruction with MATLAB, and compare the reconstructed image of the photons simulated by GEANT4 with that of the photons calculated by the geometric algorithm. The results show that the simulated one by GEANT4 is more closer to the reality than that obtained by the geometric algorithm. An executable design is also proposed at last.     

Interferometry: The tool to study giant, supergiant and Mira stars

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.     

Dichroic Filters For Astronomical X-Ray Polarimetry

We describe a programme of research to investigate materials which exhibit linear dichroism at X-ray wavelengths, and to assess their potential as astronomical X-ray polarimeters. The availability of polarising filters for X-rays would offer an efficient method of quantifying the polarisation of X-ray radiation from distant, cosmic sources. A polarising dichroic filter is expected to be a compact, low mass device which could add polarimetry capability to an instrument by being introduced into the optical path ahead of a detector. We provide estimates of sensitivity in the context of the proposed XEUS observatory, which compare favourably with those for the most promising alternative technology. We also discuss a number of astrophysical sources which are suited to polarimetric study at discrete energies offered by the X-ray dichroic filter design.     

Astrometry from Space: New Design of the GAIA Mission

An interferometric astrometric mission, aiming at accuracies at around the10 microarcsec level, was recommended as a high priority concept within thenew ESA Horizon 2000+ scientific programme. The original outline concept forsuch a mission, GAIA, presented its general feasibility but did not addressmany questions of implementation or optimisation. Another concept of aninterferometer for a scanning astrometric satellite is presented. It containsa simpler optical telescope and a more efficient detector system. The designutilizes the full resolution of all light in the dispersed fringes of aFizeau interferometer. A preliminary optimization of the satellite indicatesthat two telescope units with a baseline of 100 cm will achieve a precisionof 3, 8, 22, 68, 302 microarcsec for parallaxes of stars with V = 12, 14, 16, 18, 20 mag, respectively, from a 5 year mission. Simultaneousspectrophotometry of the entire spectrum of each star will be obtained with aresolution corresponding to intermediate band photometry. The expectedprecision of this photometry is about 0.003 mag for V = 16. The performance is good in crowded fields, at least up to one star per 5 arcsec2. A Hipparcos-type beam combiner of 150 cm width is placed in front of atelescope with 4 square apertures of 50 cm. The assumed focal length is f = 60 m and the field 0.5 degree diameter. The detector consists of CCDs used for time delayed integration (drift-scan.)     

The MPE X-ray test facility PANTER: Calibration of hard X-ray (15–50 kev) optics

The Max-Planck-Institut für extraterrestrische Physik (MPE) in Garching, Germany, uses its large X-ray beam line facility PANTER for testing X-ray astronomical instrumentation. A number of telescopes, gratings, filters, and detectors, e.g. for astronomical satellite missions like Exosat, ROSAT, Chandra (LETG), BeppoSAX, SOHO (CDS), XMM-Newton, ABRIXAS, Swift (XRT), have been successfully calibrated in the soft X-ray energy range (< 15keV). Moreover, measurements with mirror test samples for new missions like ROSITA and XEUS have been carried out at PANTER. Here we report on an extension of the energy range, enabling calibrations of hard X-ray optics over the energy range 15–50 keV. Several future X-ray astronomy missions (e.g., Simbol-X, Constellation-X, XEUS) have been proposed, which make use of hard X-ray optics based on multilayer coatings. Such optics are currently being developed by the Osservatorio Astronomico di Brera (OAB), Milano, Italy, and the Harvard-Smithsonian Center for Astrophysics (CfA), Cambridge, MA, USA. These optics have been tested at the PANTER facility with a broad energy band beam (up to 50 keV) using the XMM-Newton EPIC-pn flight spare CCD camera with its good intrinsic energy resolution, and also with monochromatic X-rays between C-K (0.277 keV) and Cu-Kα (8.04 keV). PACS: 95.55.Ka, 95.55.Aq, 41 50.+h, 07.85.Fv     

A new mask-antimask coded-aperture telescope for hard X-ray astronomy

A new imaging balloon-borne telescope for hard X-rays in the energy range from 30 to 100 keV is described. The imaging capability is provided by the use of an extended URA-based coded-mask. With only one motor and suitable stop pins, we can rotate a carbon-fiber wheel with most of the mask elements attached to it by 180°, and a bar, which is also part of the mask pattern and is allowed to rotate freely over the wheel, by 90°; this combined rotation creates an antimask of the original mask, except for the central element. This is a novel and elegant manner of providing an antimask without additional weight and complex mechanical manipulations. We show that the use of antimasks is a very effective method of eliminating systematic variations in the background map over the position-sensitive detector area. The expected sensitivity of the instrument for the 30–100 keV range is of the order of 7 × 10^-5 photons cm^-2 s^-1 keV^-1, for an integration time of 10⁴ seconds at a residual atmosphere of 3.5 g cm^-2. This telescope will provide imaging observations of bright galactic hard X-ray sources with an angular resolution of 2° in a 10° by 10° FOV, which is defined by a collimator placed in front of the detector system. We are particularly interested in the galactic center region, where recent imaging results in X-rays have shown the presence of an interesting source field. Results of computer simulations of the imaging system are reported.     

Interferometry basics in practice: Exercises

The following exercises aim to learn the link between the object intensity distribution and the corresponding visibility curves of a long-baseline optical interferometer. They are also intended to show the additional constraints on observability that an interferometer has.This practical session is meant to be carried out with the ASPRO software, from the Jean-Marie Mariotti Center, but can also be done using other observation preparation software, such as viscalc from ESO.There are two main parts with series of exercises and the exercises corrections. The first one aims at understanding the visibility and its properties by practicing with simple examples, and the second one is about UV coverage.     

孤立脉冲星的X射线光度

本文提出一种物理机制得到了孤立脉冲星的Ｘ射线光度与其自转能损失的理论关系式。它与孤立脉冲星的Ｘ射线观测数据是完全符合的。     

The VLTI – A Status Report

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.     

太阳硬X射线成像望远镜模拟研究

调制准直器型太阳硬X射线成像望远镜是目前较为通用的太阳观测设备.空间调制望远镜是基于中心轴不旋转的望远镜,适用于3轴稳定的卫星.针对我国可能的太阳观测计划,给出并比较了两组空间调制望远镜的配置方案,然后利用GEANT4高能物理通用软件模拟实际光子的计数情况,使用MATLAB实现图像重建.比较模拟光子计数得到的重建图与几...