共查询到20条相似文献，搜索用时 920 毫秒
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利用多波段同时性观测数据,研究了Blazar天体的近红外波段偏振与光学波段偏振的关系,发现两个波段的偏振度和偏振角之间都存在着很强的线性相关性．另外,两个波段的辐射流量也强烈相关．结果表明Blazr天体的近红外辐射主要来自于相对论电子的同步辐射,且与光学波段辐射来自于同一辐射区域．另外,利用2MASS数据还研究了近红外波段3个色指数J-H、H-K和J-K之间的相关性,发现J-H和H-K都与J-K强相关,但J-H与H-K之间没有相关性．最后研究了色指数-星等关系,表明在近红外波段Blazar天体变亮时谱形变平． 相似文献
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LAMOST（Large Sky Area Multi-Object Fiber Spectroscopy Telescope）的巡天战略系统的主要功能是安排观测计划,而规划巡天星表是开展所有工作的初始步骤。天文研究人员或者巡天观测人员需要从各种类型的数据库进行选星、提取和录入。使用JDBC（Java Database Connectivity）数据库访问技术,利用面向对象的编程思想,实现了一个能访问多种类型数据库、获取星表数据、数据格式转换和星表录入的工具,支持大数据量处理,为天文研究人员以及巡天观测管理人员提供帮助。 相似文献
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LAMOST(Large Sky Area Multi-Object Fiber Spectroscopy Telescope)的巡天战略系统的主要功能是安排观测计划,而规划巡天星表是开展所有工作的初始步骤。天文研究人员或者巡天观测人员需要从各种类型的数据库进行选星、提取和录入。使用JDBC(JavaDatabase Connectivity)数据库访问技术,利用面向对象的编程思想,实现了一个能访问多种类型数据库、获取星表数据、数据格式转换和星表录入的工具,支持大数据量处理,为天文研究人员以及巡天观测管理人员提供帮助。 相似文献
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利用斯隆数字巡天（SDSS）第8次释放数据（DR8）的恒星光谱数据及2MASS（Two Micro All Sky Survey）近红外点源测光数据研究著名的疏散星团NGC 6791,得到该星团的视向速度与金属丰度分别为Vr=-46.4±0.2 km·s-1和[Fe/H]=0.32±0.11dex.利用星团中红团簇巨星作为理想"标准烛光",结合2MASS近红外点源测光数据计算了该星团的绝对距离模数为（m-M）0=13.02±0.08 mag或4.02±0.15 kpc.与其他研究者给出的结果进行了比较,金属丰度、视向速度及绝对距离模数都符合得比较好.主要结论有3点:（1）NGC 6791是个极度富金属的星团;（2）在SDSS的光谱分辨能力以内,分离出的87颗团星之间不存在明显的金属丰度差异;（3）得到的距离模数对年龄、金属丰度及尘埃消光不敏感,是一种可靠的间接测量. 相似文献
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通过红外的眼睛去巡视苍穹,那些你原来已很熟悉的天体都呈现出另外一种奇异的景象。波长为2微米的全天巡查(简称2MASS)给我们提供了许多直观的天体照片,使我们的近红外天空的知识有了一个很大的扩展,也使我们得到了视觉上一种新的享受。 这次巡天工作是由美国麻省大学等使用亚利桑那的霍普金斯山和智利泛美天文台的两个一样的1.3米自动化望远镜完成 相似文献
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中国虚拟天文台图像处理分析工具（VO_IMPAT），是由国家天文台虚拟天文台项目组开发的一项服务，它提供了对数字巡天图像数据（Digital Sky Survey，DSS）、天文星表以及其他数据库的交互访问。VO_IMPAT的设计目的是实现多波段天文数据的融合。可以将不同波段的星表叠加到DSS底图上，如光学波段的USNO星表、近红外波段的2MASS星表、射电波段的NVSS星表和X射线波段的RASS星表。同时VO_IMPAT还可以对图像进行放大、缩小、伪彩色、等高线、直方图、尖锐化、平滑化、旋转等处理，不同的星表数据可以采用不同的颜色和图标显示。 相似文献
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V. E. Karachentseva S. N. Mitronova O. V. Melnyk I. D. Karachentsev 《Astrophysical Bulletin》2010,65(1):1-17
We search for isolated galaxies based on the automatic identification of isolated sources from the Two Micron All-Sky Survey
(2MASS) followed by a visual inspection of their surroundings. We use the modified Karachentseva criterion to compile a catalog
of 3227 isolated galaxies (2MIG), which contains 6% of 2MASS Extended Sources Catalog (or 2MASX) sources brighter than K
s = 12
m
with angular diameters a
K
≥ 30″. The catalog covers the entire sky and has an effective depth of z ∼ 0.02. The 2493 very isolated objects of the catalog, which we include into the 2MVIG catalog, can be used as a reference
sample to investigate the effects of the environment on the structure and evolution of galaxies located in regions with extremely
low density of matter. 相似文献
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First Mapping Observations of Two Possible Cloud Collision Candidates IRAS 02459＋6029 and 05363＋3127
Bei Xin Jun-Jie Wang 《中国天文和天体物理学报》2008,8(4)
The first mapping observations of the cold infrared sources IRAS 02459 6029 and 05363 3127 in the molecular lines 12CO(1-0), 13CO(1-0) and C18o(1-0) were made using the 13.7 m millimeter wave telescope in Qinghai. Both the integrated intensity maps and position-velocity diagrams show that each has two components adjacent in both space and velocity which means possible cloud-cloud collisions in the two regions. The near-infrared color-color diagram from the 2MASS database reveals that the density of YSOs in the colliding site is much higher than in the surrounding regions. The results appear to indicate that star forming activities have taken place in the two regions due to the cloud-cloud collision. We conclude that both sources are cloud collision candidates. 相似文献
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M. Gyulzadyan B. McLean V. Zh. Adibekyan R. J. Allen D. Kunth A. Petrosian J. A. Stepanian 《Astrophysics》2011,54(1):15-25
A database for the entire catalog of the Second Byurakan Survey (SBS) galaxies is presented. It contains new measurements
of their optical parameters and additional information taken from the literature and other databases. The measurements were
made using Ipg (near-infrared), Fpg (red), and Jpg (blue) band images from photographic sky survey plates obtained by the Palomar Schmidt telescope and extracted from the STScI
Digital Sky Survey (DSS). The database provides accurate coordinates, morphological type, spectral and activity classes, apparent
magnitudes and diameters, axial ratios and position angles, as well as number counts of neighboring objects in a circle of
radius 50 kpc. The total number of individual SBS objects in the database is now 1676. The 188 Markarian galaxies that were
re-discovered by SBS are not included in this database. We also include redshifts that are now available for 1576 SBS objects,
as well as 2MASS infrared magnitudes for 1117 SBS galaxies. 相似文献
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Tadross A. L. 《中国天文和天体物理学报》2008,8(3):362-368
As a continuation of a series of work, we aim to refine and re-determine the physical parameters of previously rarely or un-studied open star clusters with good quality CMDs using Near-IR JHK photometry. Here we present a morphological analysis of the 2MASS database (the digital "Two Micron All Sky Survey") for the open cluster Pismis 3. Some of the physical parameters are estimated for the first time, and some others, re-determined. 相似文献
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We report a new version of the “Homogeneous catalog of open cluster parameters” maintained by our team over the last decades. The catalog is based on redetermination of the main parameters of clusters (color excesses, heliocentric distances, and ages) based on published photometric measurements, in particular, those provided by the 2MASS point-source catalog. Currently, our catalog provides the parameters for 959 clusters. It also gives the estimates of cluster radial velocities for 496 clusters partly based on the data fromRAVE catalog. Estimates of proper-motion components are provided for all clusters included into the catalog. We analyze the distributions of the errors of the main cluster parameters and compare the distribution of cluster positions projected onto the Galactic plane with the distribution of cosmic masers thereby validating the distance scale of open clusters. 相似文献
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Yan-Xia Zhang Yong-Heng Zhao National Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2007,7(2):289-296
We compare the performance of Bayesian Belief Networks (BBN), Multilayer Perception (MLP) networks and Alternating Decision Trees (ADtree) on separating quasars from stars with the database from the 2MASS and FIRST survey catalogs. Having a train- ing sample of sources of known object types, the classifiers are trained to separate quasars from stars. By the statistical properties of the sample, the features important for classifica- tion are selected. We compare the classification results with and without feature selection. Experiments show that the results with feature selection are better than those without feature selection. From the high accuracy found, it is concluded that these automated methods are robust and effective for classifying point sources. They may all be applied to large survey projects (e.g. selecting input catalogs) and for other astronomical issues, such as the parame- ter measurement of stars and the redshift estimation of galaxies and quasars. 相似文献
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We describe the procedure we used to compile a catalog of the proper motions of 23 633 stars in the sky area covering about 700 square degrees at the north Galactic pole. The compiled catalog combines the data from the UCAC2, Tycho-2, and FONAC catalogs for stars down to V ～ 14 m in this sky area. In addition to proper motions, the catalog also contains the near-infrared magnitudes J, H, and K s in the 2MASS system. The mean accuracy is 2.5 mas/yr for proper motions and 0.03 m for magnitudes. 相似文献
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St. Raetz M. Va&#x;ko M. Mugrauer T.O.B. Schmidt T. Roell T. Eisenbeiss M. M. Hohle A. Koeltzsch Ch. Ginski C. Marka M. Moualla N. Tetzlaff Ch. Broeg R. Neuhuser 《Astronomische Nachrichten》2009,330(5):504-510
We report on observations of the eclipsing binary 2MASS 19090585+4911585 with the 25 cm auxiliary telescope of the University Observatory Jena. We show that a nearby brighter star (2MASS 19090783+4912085) was previously misclassified as the eclipsing binary and find 2MASS 19090585+4911585 to be the true source of variation. We present photometric analysis of VRI light curves. The system is an overcontact binary of W UMa type with an orbital period of (0.288374 ± 0.000010) d (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The absolute proper motions of about 275 million stars from the Kharkov XPM catalog have been obtained by comparing their
positions in the 2MASS and USNO-A2.0 catalogs with an epoch difference of about 45 yr for northern-hemisphere stars and about
17 yr for southern-hemisphere stars. The zero point of the system of absolute proper motions has been determined using 1.45
million galaxies. The equatorial components of the residual rotation vector of the ICRS/UCAC2 coordinate system relative to
the system of extragalactic sources have been determined by comparing the XPM and UCAC2 stellar proper motions: ω
x,y,z = (−0.06, 0.17, −0.84) ± (0.15, 0.14, 0.14) mas yr−1. These parameters have been calculated using about 1 million faintest UCAC2 stars with magnitudes R
UCAC2 > 16
m
and J > 14
m
. 7, for which the color and magnitude equation effects are negligible. 相似文献
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Zhao-Xia Han Li Zhang Department of Physics Yunnan University Kunming National Astronomical Observatories/Yunnan Observatory Chinese Academy of Sciences Kunming 《中国天文和天体物理学报》2005,5(3):256-264
The variability of γ-ray sources listed in the third EGRET catalog is studied using three variability indices. These indices are found to be statistically equivalent if the observed data are sufficiently accurate. Using the three indices,30 EGRET point sources which are positionally coincident with pulsars and 40 persistent unidentified sources at low latitudes are analyzed for their variability status. It is found that 14 of the 30 point sources may have genuine or plausible associations with pulsars, and 16 of the 40 persistent unidentified sources are possible pulsar candidates. 相似文献