近三年来我国天体测量的研究工作(英文)

该文简述近三年(2005年7月1日～2008年6月30日)我国天体测量研究工作的情况,其中包括我国天体测量工作者在仪器和归算方法、河外参考架、特别的天文研究项目,如位置、自行、三角视差和近距小质量星、太阳系、疏散星团和银河系,以及天体测量教育等方面取得的研究成果。特别描述了2007年10月在上海天文台召开的国际天文学联合会第248次讨论会的意义和作用。     

利用基本天体测量仪器开展天文测光研究

讨论有关天体测量中的测光问题，介绍一些地面天体测量仪器和空间天体测量望远镜的测光研究。给出一种测光资料的处理方法，并建议利用ＤＣＭＴ开展天文光课题研究。     

依巴谷天体测量卫星的阶段成果

本文综合介绍依巴谷天体测量卫星自１９８９年１１月开始观测以来，由头两年获得的观测资料取得的空间天体测量的阶段性成果，以及空间天体测量结果与地面观测结果相互之间的比较，成功地用于解算天体测量参数的星数已达１１２４４颗，由依巴谷天体测量卫星的头两年观测资料进行归算处理，得到恒星位置，视差和年自行的预期精度分别为３、４和２ｍａｓ。由此从整体上合面地检验了依巴谷科学计划，包括观测纲要，输入星表，卫星本身及     

第24届IAU大会决议和天体测量的前沿课题

阐明了IAU决议对天文学发展的作用，并扼要地介绍了第24届IAU大会通过的三项决议，简要评述了2000－2003年基本天体测量的前沿课题，并对我国基本天体测量未来的优先发展领域提出了几点建议。     

第二代天体测量卫星及后依巴谷地面天体测量的进展

简述了后依巴谷的天体测量工作。首先给出了第二个天体测量卫星Gaia的最新进展、最近提出的JAMSE和OBSS计划的简介,以及包含天体测量内容的SIM PlanetQuest计划的情况; 叙述了多波段天体参考架的建立和维持,特别是依巴谷星表向暗星方向的扩充和数字巡天,以及其他地面观测计划,如双星和聚星、太阳系天体的观测等;介绍了天体测量与天体物理结合的几个研究课题的进展;最后对我国自然科学基金会“十一五”天体测量优先发展的方向与内容提出建议。     

CCD探测器在地面天体测量中的应用

ＣＣＤ技术在天体测量领域的应用已得到很大发展，本文回顾了１０年来ＣＣＤ技术应用于大型望远镜和子千环上的基本情况和所取的成果，分析了这些应用中所存在的三个主要问题，并对这些问题提出了相应的解决途径，这些问题的解决，将能促进地面基本天体测量的精度和效率跨上一个新台阶。     

世纪之交空间天体测量新纪元

本文主要论述二十世纪末二十一世纪初空间天体测量新计划、新技术、以及高精度天体测量在天体物理中的应用。     

利用基本天体测量仪器开展天文测光研究(英)

讨论有关天体测量中的测光问题，介绍一些地面天体测量仪器和空间天体测量望远镜的测光研究。给出一种测光资料的处理方法，并建议利用DCMT开展天文测光课题研究。     

云南天文台基本天体测量工作的发展

介绍了云南天文台天体测量工作的发展过程，论述了在空间时代地面光学基本天体测量的必要性和应具备的条件，并且叙述了在新的要求和条件下，地面光学基本天体测量工作应该发挥的作用和广阔的发展前景。     

GAIA计划与微角秒天体测量学

欧洲空间局正在考虑的空间天体测量卫星计划（GAIA计划）将对目视星等V亮于15．5mag的5千万颗目标进行位置、自行和视差的测定,其精度为10μas,同时还对这些目标进行多色多历元光度测定．该计划可对星系距离尺度、恒星演化、银河系运动学和动力学以及参考架联结等方面进行深入研究．其开创的微角秒天体测量学亦将会对天体物理学、太阳系天体和参考架联结等方面的研究产生深远的影响．     

Galactic Astronomy in the Ultraviolet

We propose a number of prospective observational programs for the ultraviolet space observatory WSO-UV, which seem to be of great importance to modern galactic astronomy. The programs include the search for binary Cepheids; the search and detailed photometric study and the analysis of radial distribution of UV-bright stars in globular clusters (“blue stragglers”, blue horizontal-branch stars, RR Lyrae variables, white dwarfs, and stars with UV excesses); the investigation of stellar content and kinematics of young open clusters and associations; the study of spectral energy distribution in hot stars, including calculation of the extinction curves in the UV, optical and NIR; and accurate definition of the relations between the UV-colors and effective temperature. The high angular resolution of the observatory allows accurate astrometric measurements of stellar proper motions and their kinematic analysis.     

Astrophysical supplements to the ASCC‐2.5. I. Radial velocity data

We present a catalogue of radial velocities of Galactic stars with high precision astrometric data CRVAD which is the result of the cross‐identification of star lists from the General Catalog of Average Radial Velocities (GCRV) and from the homogeneous All‐sky Compiled Catalogue of 2.5Million Stars (ASCC‐2.5). The CRVAD includes accurate J2000 equatorial coordinates, proper motions and trigonometric parallaxes in the Hipparcos system, Johnson's BV photometric data, spectral types, multiplicity and variability flags from the ASCC‐2.5, and radial velocities, stellar magnitudes and spectral types from the GCRV for 34553 ASCC‐2.5 stars. The CRVAD was used for the construction of a sample of standard stars with accurate astrometric, photometric and radial velocity data for the RAVE project. A second application of the CRVAD , the radial velocity determination for 292 open clusters (including 97 with previously unknown radial velocities), using their newly defined members from proper motions and photometry in the ASCC‐2.5, is briefly described. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

The UKIDSS–2MASS proper motion survey – I. Ultracool dwarfs from UKIDSS DR4

The UK Infrared Telescope Infrared Deep Sky Survey (UKIDSS) is the first of a new generation of infrared surveys. Here, we combine the data from two UKIDSS components, the Large Area Survey (LAS) and the Galactic Cluster Survey (GCS), with Two-Micron All-Sky Survey (2MASS) data to produce an infrared proper motion survey for low-mass stars and brown dwarfs. In total, we detect 267 low-mass stars and brown dwarfs with significant proper motions. We recover all 10 known single L dwarfs and the one known T dwarf above the 2MASS detection limit in our LAS survey area and identify eight additional new candidate L dwarfs. We also find one new candidate L dwarf in our GCS sample. Our sample also contains objects from 11 potential common proper motion binaries. Finally, we test our proper motions and find that while the LAS objects have proper motions consistent with absolute proper motions, the GCS stars may have proper motions which are significantly underestimated. This is possibly due to the bulk motion of some of the local astrometric reference stars used in the proper motion determination.     

自行与银河系研究的前沿

简述了精确测定相对自行的方法,特别介绍了在用2～3个历元的底片和CCD观测结果推导恒星自行的过程中如何消除光学视场畸变、星等差和色差的具体办法;并介绍了用星系把相对自行推算绝对自行的方法。还介绍了用自行资料研究银河系结构和演化的一些前沿课题,其中包括星团研究、与银河系兼并的矮星系的发现、暗物质的检测、外星行星的探测和银河系中心黑洞的质量估算等。最后评价了自行在研究银河系中的重要性,论述了我国研制4m光学/近红外望远镜的重要意义。     

The XPM Catalogue: absolute proper motions of 280 million stars

We combined data from the Two-Micron All Sky Survey (2MASS) and USNO-A2.0 catalogues in order to derive the absolute proper motions of about 280 million stars distributed all over the sky excluding a small region near the Galactic Centre, in the magnitude range  12 < B < 19 mag  . The proper motions were derived from the 2MASS Point Sources and USNO-A2.0 catalogue positions with a mean epoch difference of about 45 years for the Northern hemisphere and about 17 years for the Southern one. The zero-point of the absolute proper motion frame (the 'absolute calibration') was specified with the use of about 1.45 million galaxies from 2MASS. Most of the systematic zonal errors inherent in the USNO-A2.0 catalogue were eliminated before the calculation of proper motions. The mean formal error of absolute calibration is less than 1 mas yr⁻¹. The XPM Catalogue will be available via CDS in Strasbourg during 2010. The generated catalogue contains the International Celestial Reference System positions of stars for the J2000 epoch, original absolute proper motions, as well as   B , R , J , H   and K magnitudes. A comparison of the proper motions obtained in this work with the data of other recent catalogues of quasars was fulfilled.     

Determination of the Proper Motions and Membership of the Globular Cluster M3 and of its Orbit in the Galaxy

We examine 14 plates of the globular cluster M3 (NGC 5272) taken with the 40 cm refractor at the Sheshan station of Shanghai Astronomical Observatory. The plates span over a period of about 77 years. The positions and absolute proper motions of eight stars in the Hipparcos Catalogue and of 49 stars in the Tycho-2 Catalogue are used as the reference frame. The astrometric reduction is made with the central overlapping principle. The absolute proper motions of 534 stars in a region of about 100' × 100' around the cluster are measured. With the new proper motion data the membership probabilities of the stars are determined. The average absolute proper motion obtained for the cluster is -0.06@0.30 mas yr-1 in R.A. and -2.6@0.30 mas yr-1 in Decl. By combining this result with the known distance and radial velocity of the cluster, we also obtained the Galactic orbit of M3 for a chosen three-component Galactic potential.     

Evolution of Population II stars

The current knowledge of the evolution of Population II stars, as observed in galactic halos and globular clusters, is outlined. The recent theoretical results provided by an improved physical understanding of the stars are reported, with a particular emphasis upon those stellar evolutionary phases which are the keystones of the interpretation of globular cluster stars. Within the up–to–date theoretical scenario, the luminosity of the turn–off stars and horizontal branch stars, which are of fundamental importance for distance and age determinations, turns out to be fainter and brighter, respectively, in comparison with previous theoretical computations. The predicted absolute magnitude of RR Lyrae stars is consistent with the bright values suggested from the long distance scale (Sandage 1993), but the slope of the relation between and metallicity ([Fe/H]) agrees with that suggested from the short distance scale (see, e.g., Carney et al. 1992, Clementini et al. 1995), at least with [Fe/H]-1.3. As to the globular cluster ages, the new computations provide younger ages ( 10 Gyr–13 Gyr), weakening the conflict with current cosmological estimates. The recent results derived from the fitting of HIPPARCOS parallaxes of field subdwarfs to the fiducial main sequence of globular clusters are consistent with the up–to–date theoretical models. However, the direct determinations of , which are based on the HIPPARCOS proper motions and trigonometric parallaxes of field RR Lyrae stars, give fainter absolute magnitudes than those obtained from the improved evolutionary models. This seems to suggest that the problem of the globular cluster distance and age is still open. Received 6 April 1998     

Kinematics and Dynamics of the Galactic Halo from RR Lyrae Variable Stars

Based on a sample of RR Lyrae variable stars including more than 9000 objects with proper motions and distances, we have investigated the kinematics of the Galactic halo from the two-dimensional velocity field. We have used both the proper motions deduced independently by us from the positional data taken from all-sky catalogues in a time interval up to 65 years and the proper motions taken from the Gaia DR2 catalogue. In addition, we have also studied the halo kinematics from the three-dimensional velocity field of ~850 RR Lyrae variables with distances, proper motions, and line-of-sight velocities. The kinematic parameters describing the velocity field have been estimated by the maximum-likelihood method; their change with Galactocentric distance has been investigated. The radial velocity dispersion in spherical coordinates σ_r ≈ 160?170 km s^?1 exceeds its values from previous papers approximately by 20 km s^?1, while the anisotropy parameter β ≈ 0.68?0.72 agrees satisfactorily with previous studies. When estimating the rotation velocity of the population of RR Lyrae stars, we identified the inner and outer halos with weak prograde and retrograde rotations, respectively.     

Globular Clusters: Absolute Proper Motions and Galactic Orbits

We cross-match objects from several different astronomical catalogs to determine the absolute proper motions of stars within the 30-arcmin radius fields of 115 Milky-Way globular clusters with the accuracy of 1–2 mas yr^?1. The proper motions are based on positional data recovered from the USNO-B1, 2MASS, URAT1, ALLWISE, UCAC5, and Gaia DR1 surveys with up to ten positions spanning an epoch difference of up to about 65 years, and reduced to Gaia DR1 TGAS frame using UCAC5 as the reference catalog. Cluster members are photometrically identified by selecting horizontal- and red-giant branch stars on color–magnitude diagrams, and the mean absolute proper motions of the clusters with a typical formal error of about 0.4 mas yr^?1 are computed by averaging the proper motions of selected members. The inferred absolute proper motions of clusters are combined with available radial-velocity data and heliocentric distance estimates to compute the cluster orbits in terms of the Galactic potential models based on Miyamoto and Nagai disk, Hernquist spheroid, and modified isothermal dark-matter halo (axisymmetric model without a bar) and the same model + rotating Ferre’s bar (non-axisymmetric). Five distant clusters have higher-than-escape velocities, most likely due to large errors of computed transversal velocities, whereas the computed orbits of all other clusters remain bound to the Galaxy. Unlike previously published results, we find the bar to affect substantially the orbits of most of the clusters, even those at large Galactocentric distances, bringing appreciable chaotization, especially in the portions of the orbits close to the Galactic center, and stretching out the orbits of some of the thick-disk clusters.