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A network flow algorithm to position tiles for LAMOST

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Research in Astronomy and Astrophysics 2009年第11期9卷 1277-1284页

作者： Guang-Wei li and gang zhao national astronomical observatories, chinese academy of sciences, beijing 100012, China national astronomical observatories Chinese Academy of Sciences

We introduce the network flow algorithm used by the Sloan Digital Sky Survey （SDSS） into the sky survey of the Large sky Area Multi-Object fiber Spectroscopic Telescope （LAMOST） to position tiles. Because fibers in LAMOST＇s focal plane are distributed uniformly, we cannot use SDSS＇ method directly. To solve this problem, firstly we divide the sky into many small blocks, and we also assume that all the targets that are in the same block have the same position, which is the center of the block. Secondly, we give a value to limit the number of the targets that the LAMOST focal plane can collect in one square degree so that it cannot collect too many targets in one small block. Thirdly, because the network flow algorithm used in this paper is a bipartite network, we do not use the general solution algorithm that was used by SDSS. Instead, we give our new faster solution method for this special network. Compared with the Convergent Mean Shift Algorithm, the network flow algorithm can decrease observation times with improved mean imaging quality. This algorithm also has a very fast running speed. It can distribute millions of targets in a few minutes using a common personal computer.

关键词： methods data analysis -- methods statistical

Planet Host Stars: Mass, Age and Kinematics

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chinese Journal of Astronomy and Astrophysics 2002年第2期2卷 151-160页

作者： Yu-Qin Chen and gang zhao national astronomical observatories, chinese academy of sciences, beijing 100012 national astronomical observatories Chinese Academy of Sciences Beijing 100012

We determine the mass, age and kinematics of 51 extra-solar planet host stars. The results are then used to search for signs of connection of the data with metallicity and to investigate the population nature. We find that the increase in mean metallicity with stellar mass is similar to that in normal field stars, so it seems unsuitable to use this relation as a constraint on the theory of planet formation. The age and kinematic distributions seem to favour the metallicity of extra-solar planet host stars being initial. Although the kinematic data of these stars indicate their origin from two populations - the thin and the thick disks, kinematics may not help in the maintenance of the planet around the host. Stars with planets, brown dwarfs or stellar companions are sorted into three groups and re-investigated separately for their formation mechanism. The main results indicate that stars with M2 0.1 and a wide period range, but there are no other differences. Thus, there does not seem to be any physically distinguishable characteristics among the three star groups.

关键词： stars: masses ages ─ stars: kinematics -planetary system

Equivalent Widths of 15 Extrasolar-Planet Host Stars

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chinese Journal of Astronomy and Astrophysics 2002年第4期2卷 377-390页

作者： gang zhao, Yu-Qin Chen and hong-Mei Qiunational astronomical observatories, chinese academy of sciences, beijing 100012 national astronomical observatories CAS NAOC Beijing 100012 China

We present the equivalent widths of 15 extrasolar-planet host stars. These data were based on the high-resolution, high signal-to-noise ratio spectra obtained with the 2.16m telescope at Xinglong station. The error in the Xinglong equivalent width is estimated by a comparison of these data with those given in previous studies of common stars.

关键词： stars: planetary systems - stars: late-type

Information from the Kinematics of F and G Stars in the Solar Neighborhood

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chinese Journal of Astronomy and Astrophysics 2002年第5期2卷 419-428页

作者： Yu-Qin Chen, gang zhao and Jian-Rong Shinational astronomical observatories, chinese academy of sciences, beijing 100012 national astronomical observatories Chinese Academy of Sciences Beijing 100012

We have calculated the orbital parameters for 90 stars in Chen et al. and updated the kinematic data for stars in Edvardsson et al. by using the accurate Hipparcos parallaxes and proper motions, and recalculated the α-element abundances in Edvardsson et al. in a way consistent with Chen et al. The two sets of data are combined in a study of stellar populations and characteristics of F & G stars in the solar neighborhood. We confirm the result of Chen et al. that a distinguishable group of stars may belong to the thick disk rather than the thin disk. The ages for the stars are determined using the theoretical isochrones of VandenBerg et al. The age-metallicity relation is investigated for different subgroups according to distance from the sun and galactic orbital parameters. It is found that a mixing of stars with different orbital parameters significantly affect the age-metallicity relation for the disk. Stars with orbits confined to the solar circle all have metallicities [Fe/H] > -0.3 irrespective of their distances from the sun or from the Galactic plane.

关键词： stars: kinematics - Galaxy: evolution - Galaxy: solar neighborhood

Spectroscopic study of globular clusters in the halo of M31 with the Xinglong 2.16 m telescope

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Research in Astronomy and Astrophysics 2011年第11期11卷 1298-1310页

作者： Zhou Fan1,2,Ya-Fang Huang1,2,Jin-Zeng li1,2,Xu Zhou1,2,Jun Ma1,2,hong Wu1,2,Tian-Meng Zhang1,2 and Yong-Heng zhao1,2 1 national astronomical observatories,chinese academy of sciences,beijing 100012,China 2 Key Laboratory of Optical Astronomy,national astronomical observatories,chinese academy of sciences,beijing 100012,China national astronomical observatories Chinese Academy of Sciences Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences

We present spectroscopic observations for 11 confirmed globular clusters(GCs) of M31 with the OMR spectrograph on the 2.16 m telescope at the Xinglong site of national astronomical observatories,chinese academy of *** of our sample clusters are located in the halo of M31 and the most remote one is out to a projected radius of 78.75 kpc from the galactic *** all our sample clusters,we measured the lick absorption-line indices and radial *** is noted that most GCs in our sample are distinct from the HI rotation curve of galaxy M31,especially for B514,MCGC5,H12 and B517,suggesting that most of our sample clusters do not have a kinematic association with the star-forming young disk of the *** separately fitted the absorption line indices from the updated stellar population model of Thomas et *** two different tracks of Cassisi and Padova,by applying the χ2 minimization *** fitting results show that all our sample clusters are older than 10 Gyr,and metal-poor(2.38 ≤ [Fe/H] ≤ 0.91 dex).After merging the spectroscopic metallicity of our work with the previously published ones,we extended the cluster sample out to a projected radius of 117 kpc from the galaxy's *** found the metallicity gradient exists for all the confirmed clusters with a slope of 0.028 ± 0.001 dex kpc ***,the slope turns out to be 0.018 ± 0.001 dex kpc 1 for all the halo clusters,which is much *** we only consider the outer halo clusters with rp > 25 kpc,the slope becomes 0.010 ± 0.002 dex kpc 1 and if one cluster G001 is excluded from the outer halo sample,the slope is 0.004 ± 0.002 dex kpc ***,we conclude that the metallicity gradient for M31's outer halo clusters is not significant,which agrees well with previous findings.

关键词： galaxies individual(M31) — galaxies star clusters — globular clusters general — star clusters general

Design, performance and application of a line-imaging velocity interferometer system for any reflector coupled with a streaked optical pyrometer system at the Shenguang-Ⅱ upgrade laser facility

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High Power Laser Science and Engineering 2024年第1期12卷 52-59页

作者： Dawei Yuan Shaojun Wang Huigang Wei Haochen Gu Yu Dai Jiayong Zhong Yutong li gang zhao Jie Zhang Key Laboratory of Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijingChina Institute of Frontiers in Astronomy and Astrophysics of beijing Normal University BeijingChina beijing national Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijingChina Key Laboratory for Laser Plasmas(MOE)and School of Physics and Astronomy Shanghai Jiao Tong UniversityShanghaiChina Department of Astronomy Beijing Normal UniversityBeijingChina Collaborative Innovation Center of IFSA Shanghai Jiao Tong UniversityShanghaiChina School of Physical sciences University of Chinese Academy of SciencesBeijingChina Songshan Lake Materials Laboratory DongguanChina

The velocity interferometer system for any reflector(VISAR) coupled with a streaked optical pyrometer(SOP) system is used as a diagnostic tool in inertial confinement fusion(ICF) experiments involving equations of state and shock *** validate the process of adiabatically compressing the fuel shell through precise tuning of shocks in experimental campaigns for the double-cone ignition(DCI) scheme of ICF, a compact line-imaging VISAR with an SOP system is designed and implemented at the Shenguang-II upgrade laser facility. The temporal and spatial resolutions of the system are better than 30 ps and 7 μm, respectively. An illumination lens is used to adjust the lighting spot size matching with the target size. A polarization beam splitter and λ/4 waveplate are used to increase the transmission efficiency of our system. The VISAR and SOP work at 660 and 450 nm, respectively, to differentiate the signals from the scattered lights of the drive lasers. The VISAR can measure the shock velocity. At the same time, the SOP system can give the shock timing and relative strength. This system has been used in different DCI campaigns, where the generation and propagation processes of multi-shock are carefully diagnosed.

关键词： double-cone ignition streaked optical pyrometer velocity interferometer system for any reflector

Metallicity calibration for solar type stars based on red spectra

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Research in Astronomy and Astrophysics 2011年第5期11卷 563-576页

作者： Jing-Kunzhao gangzhao Yu-QinChen A-liLuo KeyLaboratoryofOpticalAstronomy NationalAstronomicalObservatoriesChineseAcademyofSciencesBeijing100012China

Based on a high resolution and high signal-to-noise ratio （S/N） spectral analysis of 90 solar-type stars, we have established several new metaUicity calibrations in the Tefr range [5600, 6500] K based on red spectra with the wavelength range of 560-880 nm. The new metallicity calibrations are applied to determine the metallicity of solar analogs selected from Sloan Digital Sky Survey （SDSS） spectra. There is a good consistent result with the adopted value presented in SDSS-DR7 and a small scatter of 0.26 dex for stars with S/N 〉 50 being obtained. This study provides a new reliable way to derive the metallicity for solar-like stars with low resolution spectra. In particular, our calibrations are useful for finding metal-rich stars, which are missing in the SEGUE Stellar Parameter Pipeline.

关键词： techniques: radial velocities - stars: temperatures - stars: abundances

The periodicity of 3C 273's radio light curve at 15 GHz found by the wavelet method

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Science China(Physics,Mechanics & Astronomy) 2010年第S1期53卷 252-255页

作者： ZHANG HaoJing1,2,zhao gang1,ZHANG Xiong3 & BAI JinMing4 1 national astronomical observatories,chinese academy of sciences,beijing 100012,China 2 Graduate University of chinese academy of sciences,beijing 100049,China 3 Department of Physics,Yunnan Normal Univeristy,Kunming 650092,China 4 national astronomical observatories/Yunnan Observatory,chinese academy of sciences,Kunming 650011,China national astronomical observatories Chinese Academy of Sciences Beijing China Graduate University of chinese academy of sciences Beijing China Department of Physics Yunnan Normal Univeristy Kunming China national astronomical observatories/ Yunnan Observatory Chinese Academy of Sciences Kunming China

We analyze the radio light curve of 3C 273 at 15 GHz from 1963 to 2006 taken from the database of the literature,and find evidence of quasi-periodic *** the wavelet analysis method to analyze these data,our results indicate that:(1) There is one main outburst period of P1=8.1±0.1 year in 3C *** period is in a good agreement with Ozernoi's analysis in optical bands.(2) Based on the possible periods,we expect the next burst in 2014 October.

关键词： quasar object individual(3C 273) radio band’s periodicity analysis wavelet method

Spectral analysis of two solar twins and the colors of the Sun

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Science China(Physics,Mechanics & Astronomy) 2010年第8期53卷 579-585页

作者： zhao ZhengShi1,2, CHEN YuQin1, zhao JingKun1 & zhao gang1 1 national astronomical observatories, chinese academy of sciences, beijing 100012, China 2 Graduate University of chinese academy of sciences, beijing 100049, China national astronomical observatories Chinese Academy of Sciences Graduate University of chinese academy of sciences

High resolution (R^40,000) and high signal-to-noise ratio (>150) spectra of two solar twins, HD146233 and HD195034, are obtained with the Coude Echelle Spectrograph at the 2.16 m telescope of the national astronomical observatories of chinese academy of sciences (Xinglong, China). Based on the detailed spectrum match, comparisons of chemical composition and chromospheric activity, HD146233 and HD195034 are confirmed that they are similar to the Sun except for lithium abundance, which is higher than the solar value. Moreover, among nine solar twin candidates (including HD146233 and HD195034) found in the previous works, we have picked out six good solar twin candidates based on newly-derived homogenous parameters, and collected their colors in the Johnson/Cousins, Tycho, 2MASS and Strmgren system from the literature. The average color are (B-V)⊙=0.644 mag, (V-Ic)⊙=0.707 mag, (BT-VT)⊙=0.725 mag, (J-H)⊙=0.288 mag, (H-K)⊙=0.066 mag, (v-y)⊙=1.028 mag, (v-b)⊙=0.619 mag, (u-v)⊙=0.954 mag and (b-y)⊙=0.409 mag, which represent the solar colors with higher precision than previous works.

关键词： Sun-colors Star-atmospheres abundances fundamental parameters

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