NUV Star Catalog from the Lunar-based Ultraviolet Telescope Survey: First Release

We present a star catalog extracted from the Lunar-based Ultraviolet Telescope （LUT） survey program. LUT＇s observable sky area is a circular belt around the Moon＇s north pole, and the survey program covers a preferred area of about 2400 deg2 which includes a region of the Galactic plane. The data are processed with an automatic pipeline which copes with stray light contamination, artificial sources, cosmic rays, flat field calibration, photometry and so on. In the first release version, the catalog provides high confidence sources which have been cross-identified with the Tycho-2 catalog. All the sources have signalto-noise ratio larger than 5, and the corresponding magnitude limit is typically 14.4 mag, but can be as deep as -16 mag if stray light contamination is at the lowest level. A total of 86 467 stars are recorded in the catalog. The full catalog in electronic form is available online.

The Fifth Edition of the General Catalogue of Variable Stars:experiences in the constellation Centaurus

We have recently announced that the General Catalogue of Variable Stars enters the stage of its fifth, purely electronic edition （GCVS 5.1）. We have included 1408 variable stars in the constellation Centaurus in this new version, GCVS 5.1. Working on this revision, we applied current possibilities from data mining, suggested new variability types for many variable stars and found new light elements for a large number of periodic variables. This paper describes the work completed during the preparation of GCVS 5.1 for Centaurus and discusses in detail a number of the most astrophysically significant cases.

Life Origin in the Milky Way Galaxy: II. Scanning for Habitable Stellar Systems on Behalf of Future Space Missions

The possibility of the life origin in the stellar systems, located at a distance of ~200 pc from the solar system, was investigated. The stars, in the spectrums of which C (carbon), O (oxygen), N (nitrogen), and P (phosphorus) are found, are called DNA-stars. Based on stellar abundances a new method for searching for habitable exoplanets has been developed and a list of 48 DNA-stars in the solar neighborhood, on which life is possible, has been defined. The quota of DNA-stars is equal 1.3% of the total amount of Hypatia Stellar Catalog. Only three DNA-stars out of selected 48 stars belong to the spectral class as our Sun (G2V). The closest to the solar system is the DNA-star with the number HIP 15510, which belongs to the G8V class and is 6 pc away from the solar system. Nine DNA-stars, which have the highest chemical similarity with solar spectrum, were identified. It is identified that one of these nine stars, HIP 24681, has six planets.

A catalog of DB white dwarfs from the LAMOST DR5 and construction of templates

In this study, we employ machine learning to build a catalog of DB white dwarfs(DBWDs) from the LAMOST Data Release(DR) 5. Using known DBs from SDSS DR14, we selected samples of highquality DB spectra from the LAMOST database and applied them to train the machine learning process.Following the recognition procedure, we chose 351 DB spectra of 287 objects, 53 of which were new identifications. We then utilized all the DBWD spectra from both SDSS DR14 and LAMOST DR5 to construct DB templates for LAMOST 1 D pipeline reductions. Finally, by applying DB parameter models provided by D. Koester and the distance from Gaia DR2, we calculated the effective temperatures, surface gravities and distributions of the 3 D locations and velocities of all DBWDs.

M-giant star candidates identified in LAMOST DR 1

We perform a discrimination procedure with the spectral index diagram of TiO 5 and Ca H2＋Ca H3 to separate M giants from M dwarfs. Using the M giant spectra identified from LAMOST DR1 with high signal-to-noise ratio, we have successfully assembled a set of M giant templates, which show more reliable spectral features. Combining with the M dwarf/subdwarf templates in Zhong et al., we present an extended library of M-type templates which includes not only M dwarfs with a well-defined temperature and metallicity grid but also M giants with subtypes from M0 to M6. Then, the template-fitting algorithm is used to automatically identify and classify M giant stars from LAMOST DR1. The resulting catalog of M giant stars is cross-matched with 2MASS J H Ks and WISE W1/W2 infrared photometry. In addition, we calculated the heliocentric radial velocity of all M giant stars by using the cross-correlation method with the template spectrum in a zero-velocity rest frame.Using the relationship between the absolute infrared magnitude MJ and our classified spectroscopic subtype, we derived the spectroscopic distance of M giants with uncertainties of about 40%. A catalog of 8639 M giants is provided. As an additional result of this analysis, we also present a catalog of 101 690 M dwarfs/subdwarfs which are processed by our classification pipeline.

Validation of LAMOST stellar parameters with the PASTEL catalog

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope （LAMOST） published its first data release （DR1） in 2013, which is currently the largest dataset of stellar spectra in the world. We combine the PASTEL catalog and SIMBAD radial velocities as a testing standard to validate stellar parameters （effec- tive temperature Tefr, surface gravity log g, metallicity [Fe/H] and radial velocity Vr） derived from DR1. Through cross-identification of the DR1 catalogs and the PASTEL catalog, we obtain a preliminary sample of 422 stars. After removal of stellar param- eter measurements from problematic spectra and applying effective temperature con- straints to the sample, we compare the stellar parameters from DR1 with those from PASTEL and SIMBAD to demonstrate that the DR1 results are reliable in restricted ranges of Tefr. We derive standard deviations of 110 K, 0.19 dex and 0.11 dex for Tell, log 9 and [Fe/H] respectively when Teff〈 8000 K, and 4.91 km s-1 for Vr when Teff 〈 10 000 K. Systematic errors are negligible except for those of Vr. In addition, metallicities in DR1 are systematically higher than those in PASTEL, in the range of PASTEL [Fe/H] 〈 -1.5.

M Dwarf catalog of LAMOST general survey data release one

We present a spectroscopic catalog of 93 619 M dwarfs from the first data release of the Large Sky Area Multi-Object Fiber Spectroscopic Telescope（LAMOST）general survey. During sample selection, M giant contamination was eliminated using2 MASS photometry and Ca H/TiO molecular indices. For each spectrum, the spectral subtype and values are provided including radial velocity, Hα equivalent width, a series of prominent molecular band indices, and the metal–sensitive parameter ζ, as well as distances and the space motions for high S/N objects. In addition, Hα emission lines are measured to examine the magnetic activity properties of M dwarfs and 7179 active ones are found. In particular, a subsample with significant variation in magnetic activity is revealed through observations from different epochs. Finally, statistical analysis for this sample is performed, including the metallicity classification, the distribution of molecular band indices and their errors.

Light curve solutions of six eclipsing binaries at the lower limit of periods for W UMa stars

Photometric observations are presented in V and I bands of six eclipsing binaries at the lower limit of the orbital periods for W UMa stars. Three of them are newly discovered eclipsing systems. The light curve solutions reveal that all shortperiod targets are contact or overcontact binaries and six new binaries are added to the family of short-period systems with estimated parameters. Four binaries have com- ponents that are equal in size and a mass ratio near 1. The phase variability shown by the V-I colors of all targets may be explained by lower temperatures on their back surfaces than those on their side surfaces. Five systems exhibit the O＇Connell effect that can be modeled by cool spots on the side surfaces of their primary components. The light curves of V1067 Her in 2011 and 2012 are fitted by diametrically opposite spots. Applying the criteria for subdivision of W UMa stars to our targets leads to ambiguous results.

Candidate members of star clusters from LAMOST DR2

In this work, we provide 2189 photometrically- and kinematically-selected candidate members of 24 star clusters from the LAMOST DR2 catalog. We perform two-step membership identification： selection along the stellar track in the colormagnitude diagram, i.e., photometric identification, and selection from the distribution of radial velocities, i.e. the kinematic identification. We find that the radial velocities from the LAMOST data are very helpful in the membership identification. The mean probability of membership is 40% for the sample selected with radial velocity. With these 24 star clusters, we investigate the performance of the radial velocity and metallicity estimated with the LAMOST pipeline. We find that the systematic offsets in radial velocity and metallicity are 0.85 ± 1.26 km s-1and-0.08 ± 0.04 dex, with dispersions of 5.47＋1.16-0.71 km s-1and 0.13＋0.04-0.02 dex, respectively. Finally, we propose that the photometrically-selected candidate members of the clusters covered by the LAMOST footprint should be assigned higher priority so that more candidate stars can be observed.

Astrophysical parameters of ten poorly studied open star clusters

We present the fundamental parameters of ten open star clusters, nominated from Kronberger et al. who presented some newly discovered stellar groups on the basis of the Two Micron All Sky Survey photometry and Digitized Sky Survey visual images. Star counts and photometric parameters （radius, membership, distance, color excess, age, luminosity function, mass function, total mass, and dynamical relaxation time） have been determined for these ten clusters for the first time. In order to calibrate our procedures, the main parameters （distance, age, and color excess） have been reestimated for another five clusters, which are also studied by Kronberger et al.

Database of molecular masers and variable stars

We present the database of maser sources in H2 O, OH and Si O lines that can be used to identify and study variable stars at evolved stages. Detecting the maser emission in H2 O, OH and Si O molecules toward infrared-excess objects is one of the methods for identifing long-period variables(LPVs, including miras and semiregulars), because these stars exhibit maser activity in their circumstellar shells. Our sample contains 1803 known LPV objects. Forty-six percent of these stars(832 objects) manifest maser emission in the line of at least one molecule: H2 O, OH or Si O. We use the database of circumstellar masers in order to search for LPVs which are not included in the General Catalogue of Variable Stars(GCVS). Our database contains 4806 objects(3866 objects without associations in GCVS) with maser detection in at least one molecule. Therefore it is possible to use the database in order to locate and study the large sample of LPV stars. The database can be accessed at http://maserdb.net.

数字天顶测量匹配星表的选取

为了进一步提升以数字天顶望远镜为代表的天文定位定向精度,提出一种数字天顶测量匹配星表的选取方法:指出研究不同星表系统之间的差异及其对天文测量的影响对提升数字照相天顶望远镜(DZT)的精度意义重大;并利用丽江站数字天顶望远镜测量数据,以盖亚(GAIA)DR2为基础研究第谷2号(Tycho-2)星表的位置误差及自行误差、视差、视向速度及星点密度对天文大地测量的影响。结果表明,相较于位置误差、自行误差、视差及视向速度等因素,GAIA DR2星点密度的增加对测量精度的提升更为显著,采用星点密度更高的GAIA DR2星表可以使得数字天顶测量的天文经纬度精度提升约20%。研究结果可为提高天文坐标测量、垂线偏差测量、世界时(universial time)UT1测量等的精度提供参考。

小天体附着装置地形被动自适应机构设计与优化

面向在小天体非确知、非结构性表面安全稳定附着的技术需求,设计了一种可同时在偏移和扭转共6个自由度上实现对抓附区域星表地形被动自适应的串并混联机构,并完成了其工作空间优化。首先,针对附着过程中附着装置与星表拟合球面不居中问题,提出了一种3-RSPS串并混联被动自适应机构设计方案;进而,采用修正的G-K公式计算了该机构的自由度,基于空间位置矢量法推导出其逆运动学模型,并通过虚拟样机仿真验证了逆运动学模型的正确性;最后,采用数值搜索方法完成了该机构的定姿态工作空间分析和基于NSGA-II算法的多目标优化。结果表明:相较于目前广泛应用的3-SPS并联机构,本文所设计的星表地形自适应机构的全局工作空间提高了40.9%,优化后,又进一步提高了21.3%,可适应更加崎岖陡峭的小天体星表地形,具有较好的工程价值。

适用于星敏感器的导航星星库制定

导航星星库对星图识别、最终姿态获取具有重要意义。导航星星库的容量 ,存储方式 ,存储内容 ,读取方式 ,是影响星图识别的识别时间和识别率的关键因素。本文介绍了采用球矩阵存储和读取导航星库的方法 ,阐述了导航星的选取规则及存储内容。球矩阵方法可以在全天球范围内快捷查找导航星的大致区域 ;年中平位置及导航星星对角距的存储 ,可使视位置转换时间及星图识别时间进一步减少。

一种新的导航星选取算法研究

在导航星表的建立过程中 ,由于恒星的数量太多 ,往往要进行筛选 ,通常这种选择复杂费时 ,而结果往往并不是最优的。本文引入了动态星等阈值分布函数 ,将传统星等阈值过滤算法中的静态阈值用动态星等阈值代替 ,建立了一种新的动态星等阈值过滤选择模式。而基于统计学习理论的支持向量机方法为求解高维非线性动态星等阈值分布函数提供了新的途径。本文讨论了这种基于支持向量机的导航星自动选择算法——回归选取算法。实验表明 ,用该算法所选取的导航星表 ,导航星数量少、分布均匀性好。同时它还能适应多种任务的导航星选取要求 ,具有很强的通用性。

适用于小视场星敏感器的导航星表构建方法

导航星表构建是星敏感器设计阶段的重要工作。对于小视场,受限于恒星分布规律,易出现导航星表"空洞"问题。为解决小视场条件下均匀完备导航星表构建问题,对基于球面螺旋基准点的导航星表构建方法进行了改进:摒弃了原方法通过改变球面螺旋基准点数量和位置重新构建导航星表的思路,转而通过增选部分恒星来达到减少星表"空洞"的目的。设立了描述恒星消除星表"空洞"能力的权值,并以该权值递减顺序开展恒星增选;同时,设计了增选恒星距离阈值条件以保持增选后导航星表的均匀性。仿真表明,在4°圆形视场条件下,相对于原方法,文中方法得到的导航星表,总星数减少708颗,均匀性指标提高约44%,而星表"空洞"变化较小,显示了较好的性能。

适用于星敏感器的星图识别方法

采用星敏感器测卫星姿态是现行方法中精度最高的 ,其关键是星图识别。阐述了只采用观测星的位置信息 ,利用观测星图与导航星表的星对角距进行聚类匹配 ,根据观测星图的连通性进行匹配识别的方法 ;用图论理论解释了星识别过程 ;介绍了导航星的选取规则、导航星库的存储内容及采用球矩阵存储和读取导航星库的方法 ;用 1 2 0 MHz主频的微机模拟分析了门限和位置噪声对识别及识别时间的影响。在门限取 0 .0 5°,位置噪声 (单轴 )δ=0 .0 2°以下时 ,在任一区域的识别率达 1 0 0 % ,识别时间平均少于 0 .2 s。

国外红外天文望远镜发展现状

介绍美国、欧洲、日本典型的红外巡天计划及其红外天文望远镜,包括携带的仪器设备、工作状态和望远镜的光学结构特性。分析了红外探测器件的性能以及红外巡天计划生成的星表数据。展望了国外红外天文望远镜的发展趋势。

红外星表在地基红外辐射测量系统中的应用

国内已知的红外星库数量有限，辐射照度、覆盖波段范围小，分布密集度低，无法满足现有地基红外辐射测量系统天文标定的需要。根据系统的探测波段考察并选取IRAS、2MASS、WISE、AKARI 4个全空域巡天计划及其生成的红外星表。综合考虑大气弥散、大气衰减的影响，分析计算系统在短波红外1~3μm、中波红外3~5μm、长波红外8~10μm的极限探测能力及在对应点源星表中的最低可探测的星等。搜索选取可供系统观测的恒星，结果显示在短波选取4599个恒星目标，中波选取125个恒星目标，长波选取1个恒星目标，为我国现有地基红外辐射测量系统天文标定及红外星表进一步应用提供理论依据。

弹载导航星表的设计与实现

根据弹道导弹飞行时间短,飞行姿态相对稳定的特性,提出了一种弹载导航星表的设计方法。分析了导弹飞行轨迹投影的特点,其在天球上投影为大圆,在地心惯性坐标系XOY平面上的投影为椭圆,并对飞行轨迹进行分类。根据限制条件,确定出星敏感器扫描的视场区域,挑选出视场中的恒星,构建出弹载导航星表,并与传统的三角形星表进行比较。仿真结果表明,该方法简单、易行,存储容量较小,同时避免了在两极的情况下,赤经难以表示的问题。减少了星图识别时间,提高了星光制导的数据输出率,满足了星光制导在弹道导弹上应用的要求。