检索结果-南通市图书馆

Planet Host Stars: Mass, Age and Kinematics

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

学校读者我要写书评

暂无评论

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

Metallicity calibration for solar type stars based on red spectra

在线全文

学校读者我要写书评

暂无评论

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

An Analysis of the Condensation Temperature of Elements of Extrasolar Planetary Systems

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2005年第6期5卷 619-626页

作者： Cong Huang gang zhao Hua-Wei Zhang yu-qin chen Department of Astronomy Peking University Beijing 100871 National astronomical observatories Chinese Academy of Sciences Beijing 100012

Using high signal-to-noise ratio spectra of extrasolar planet-hosting stars, we obtained the atmospheric parameters, accurate metallicities and the differential abundance for 15 elements （C, O, Na, Mg, Al, Si, S, Ca, Sc, Ti, V, Cr, Mn, Ni and Ba）. In a search for possible signatures of metal-rich material accreting onto the parent stars, we found that, for a given element, there is no significant trend of increasing [X/H] with increasing condensation temperature To. In our sample of planet-harboring stars, the volatile and refractory elements behave similarly, and we can not confirm if there exists any significant dependence on the condensation temperature Tc.

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

Automatic Normalization and Equivalent-Width Measurement of High-Resolution Stellar Spectra

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2006年第6期6卷 689-696页

作者： Jing-Kun zhao gang zhao yu-qin chen Jian-Rong Shi yu-Juan Liu Ju-Yong Zhang National astronomical observatories Chinese Academy of Sciences Beijing 100012

It is well known that normalization, radial velocity correction and equivalent-width measurement of high-resolution stellar spectra are time-consuming work. In order to improve the efficiency we present an automatic method for these routines. The continuum is determined by fitting the ＇high points＇ in the spectrum. After continuum normalization, the program automatically searches for the position of the Ha line and obtains a rough radial velocity, then computes an accurate radial velocity by cross-correlation between the given spectrum and the solar spectrum. In this method, the equivalent-width is automatically measured using Gaussian fitting. A comparison between our results and those from traditional analysis shows that the typical error for equivalent width is around 3.8% in our method. Developing such automatic routines does not mean to replace the interactive reduction method： it is just for a quick extraction of information from the spectra, especially those obtained in large sky surveys.

关键词： techniques radial velocities - stars abundances

Stellar Abundance and Galactic Chemical Evolution through LAMOST Spectroscopic Survey

在线全文

学校读者我要写书评

暂无评论

chinese Journal of Astronomy and Astrophysics 2006年第3期6卷 265-280页

作者： gang zhao yu-qin chen Jian-Rong Shi Yan-Chun Liang Jin-Liang Hou Li chen Hua-Wei Zhang Ai-Gen Li National astronomical observatories Chinese Academy of Sciences Beijing 100012 Shanghai astronomical Observatory Chinese Academy of Sciences Shanghai 200030 Department of Astronomy School of Physics Peking University Beijing 100871 Department of Physics and Astronomy University of Missouri Columbia MO 65211 USA

A project of a spectroscopic survey of Galactic structure and evolution with a Large sky Area Multi-Object fiber Spectroscopic Telescope （LAMOST） is presented. The spectroscopic survey consists of two observational modes for various targets in our Galaxy. One is a major survey of the Milky Way aimed at a systematic study of the stellar abundance and Galactic chemical evolution through low resolution （R = 1000 2000） spectroscopy. Another is a follow-up observation with medium resolution （R = 10000） spectrographs aimed at detailed studies of the selected stars with different chemical composition, kinematics and dynamics.

关键词： techniques: spectroscopic - stars: abundances - Galaxy: structure - Galaxy:abundances - Galaxy: kinematics and dynamics - Galaxy: evolution

Chemical abundance analysis of 19 barium stars

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2016年第1期16卷 159-174页

作者： Guo-Chao Yang Yan-Chun Liang Monique Spite yu-qin chen gang zhao Bo Zhang Guo-qing Liu yu-Juan Liu Nian Liu Li-Cai Deng Francois Spite Vanessa Hill Cai-Xia Zhang College of Physics and Information Engineering Hebei Normal University Shijiazhuang 050024 China Key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100012 China University of chinese academy of sciences Beijing 100049 China GEPI Observatoire de Paris-Meudon 92195 Meudon France Physics Department and Tsinghua Center for Astrophysics Tsinghua University Beijing 100084 China Astronomy Department Beijing Normal University Beijing 100875 China Department of Physics Shijiazhuang University Shijiazhuang 050035 China

We aim at deriving accurate atmospheric parameters and chemical abundances of 19 barium（Ba） stars, including both strong and mild Ba stars, based on the high signal-to-noise ratio and high resolution Echelle spectra obtained from the 2.16 m telescope at Xinglong station of National astronomical observatories, chinese academy of sciences. The chemical abundances of the sample stars were obtained from an LTE, plane-parallel and line-blanketed atmospheric model by inputting the atmospheric parameters（effective temperatures Teff, surface gravities log g, metallicity [Fe/H] and microturbulence velocity ξt） and equivalent widths of stellar absorption lines. These samples of Ba stars are giants as indicated by atmospheric parameters, metallicities and kinematic analysis about UVW velocity. Chemical abundances of 17 elements were obtained for these Ba stars. Their Na, Al, α- and iron-peak elements（O, Na, Mg, Al, Si, Ca,Sc, Ti, V, Cr, Mn, Ni） are similar to the solar abundances. Our samples of Ba stars show obvious overabundances of neutron-capture（n-capture） process elements relative to the Sun. Their median abundances of[Ba/Fe], [La/Fe] and [Eu/Fe] are 0.54, 0.65 and 0.40, respectively. The Y I and Zr I abundances are lower than Ba, La and Eu, but higher than the α- and iron-peak elements for the strong Ba stars and similar to the iron-peak elements for the mild stars. There exists a positive correlation between Ba intensity and [Ba/Fe].For the n-capture elements（Y, Zr, Ba, La）, there is an anti-correlation between their [X/Fe] and [Fe/H]. We identify nine of our sample stars as strong Ba stars with [Ba/Fe]〉0.6 where seven of them have Ba intensity Ba=2-5, one has Ba=1.5 and another one has Ba=1.0. The remaining ten stars are classified as mild Ba stars with 0.17〈[Ba/Fe]〈0.54.

关键词： methods: observational - stars: abundances - stars: atmospheres - stars: chemically peculiar- stars: kinematics and dynamics - stars: late-type

Emerging contaminants:A One Health perspective

在线全文

学校读者我要写书评

暂无评论

The Innovation 2024年第4期5卷 140-170,139页

作者： Fang Wang Leilei Xiang Kelvin Sze-Yin Leung Martin Elsner Ying Zhang yuming Guo Bo Pan hongwen Sun Taicheng An Guangguo Ying Bryan WBrooks Deyi Hou Damian EHelbling Jianqiang Sun Hao Qiu Timothy MVogel Wei Zhang Yanzheng Gao Myrna JSimpson Yi Luo Scott XChang Guanyong Su Bryan MWong Tzung-May Fu Dong Zhu Karl JJobst chengjun Ge Frederic Coulon Jean Damascene Harindintwali Xiankui Zeng Haijun Wang yuhao Fu Zhong Wei Rainer Lohmann Changer chen Yang Song Concepcion Sanchez-Cid yu Wang Ali El-Naggar Yiming Yao Yanran Huang Japhet Cheuk-Fung Law chenggang Gu Huizhong Shen Yanpeng Gao Chao qin Hao Li Tong Zhang Natàlia Corcoll Min Liu Daniel SAlessi Hui Li Kristian KBrandt Yolanda Pico cheng Gu Jianhua Guo Jianqiang Su Philippe Corvini Mao Ye Teresa Rocha-Santos Huan He Yi Yang meiping Tong Weina Zhang Fidèle Suanon Ferdi Brahushi Zhenyu Wang Syed AHashsham Marko Virta qingbin yuan Gaofei Jiang Louis A.Tremblay qingwei Bu Jichun Wu Willie Peijnenburg Edward Topp Xinde Cao Xin Jiang Minghui Zheng Taolin Zhang Yongming Luo Lizhong Zhu Xiangdong Li DamiàBarceló Jianmin chen Baoshan Xing Wulf Amelung Zongwei Cai Ravi Naidu Qirong Shen Janusz Pawliszyn Yong-guan Zhu Andreas Schaeffer Matthias C.Rillig Fengchang Wu gang yu James M.Tiedje State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil ScienceChinese Academy of SciencesNanjing 210008China University of chinese academy of sciences Beijing 100049China Department of Chemistry Hong Kong Baptist UniversityHong KongChina HKBU Institute of Research and Continuing Education Shenzhen Virtual University ParkShenzhenChina Technical University of Munich TUM School of Natural SciencesInstitute of Hydrochemistry85748 GarchingGermany School of Resources&Environment Northeast Agricultural UniversityHarbin 150030China Climate Air Quality Research UnitSchool of Public Health and Preventive MedicineMonash UniversityMelbourneVICAustralia Faculty of Environmental Science&Engineering Kunming University of Science&TechnologyKunming 650500China Ministry of Education Key Laboratory of Pollution Processes and Environmental Criteria College of Environmental Science and EngineeringNankai UniversityTianjin 300350China Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control School of Environmental Science and EngineeringInstitute of Environmental Health and Pollution ControlGuangdong University of TechnologyGuangzhou 510006China Ministry of Education Key Laboratory of Environmental Theoretical Chemistry South China Normal UniversityGuangzhouGuangdong 510006China Department of Environmental Science Baylor UniversityWacoTXUSA Center for Reservoir and Aquatic Systems Research(CRASR) Baylor UniversityWacoTXUSA School of Environment Tsinghua UniversityBeijing 100084China School of Civil and Environmental Engineering Cornell UniversityIthacaNY 14853USA Key Laboratory of Microbial Technology for Industrial Pollution Control of Zhejiang Province Zhejiang University of TechnologyHangzhou 310014China School of Environmental Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Laboratoire d’Ecologie Microbienne Universite Claude Bernard Lyon 1UMR CNRS 5557UMR INRAE 1418VetAgro Sup69622 VilleurbanneFrance Department of Pla

Environmental pollution is escalating due to rapid global development that often prioritizes human needs over planetary *** global efforts to mitigate legacy pollutants,the continuous introduction of new substances remains a major threat to both people and the *** response,global initiatives are focusing on risk assessment and regulation of emerging contaminants,as demonstrated by the ongoing efforts to establish the UN’s Intergovernmental Science-Policy Panel on Chemicals,Waste,and Pollution *** review identifies the sources and impacts of emerging contaminants on planetary health,emphasizing the importance of adopting a One Health *** for monitoring and addressing these pollutants are discussed,underscoring the need for robust and socially equitable environmental policies at both regional and international *** actions are needed to transition toward sustainable pollution management practices to safeguard our planet for future generations.

关键词： pollution planet contaminants

Sky subtraction for LAMOST

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2017年第9期17卷 25-38页

作者： Zhong-Rui Bai Hao-Tong Zhang Hai-Long yuan Guang-Wei Li Jian-Jun chen Ya-Juan Lei Hui-qin Yang Yi-Qiao Dong gang Wang Yong-Heng zhao 1 University of chinese academy of sciences Beijing 100049China Key Lab for Optical Astronomy National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China

Sky subtraction is a key technique in data reduction of multi-fiber spectra. Knowledge of characteristics related to the instrument is necessary to determine the method adopted in sky subtraction. In this study, we describe the sky subtraction method designed for the Large sky Area Multi-Object fiber Spectroscopic Telescope （LAMOST） survey. The method has been integrated into the LAMOST 2D Pipeline v2.6 and applied to data from LAMOST DR3 and later. For LAMOST, calibration using sky emission lines is used to alleviate the position-dependent （and thus time-dependent） ,-~ 4% fiber throughput uncertainty and small wavelength instability （0.1/~） during observation. Sky subtraction using principal component analysis （PCA） further reduces 25% of the sky line residual from OH fines in the red part of LAMOST spectra after the master sky spectrum, which is derived from a B-spline fit of 20 sky fibers in each spectrograph. Using this approach, values are adjusted by a sky emission line and subtracted from each fiber. Further analysis shows that our wavelength calibration accuracy is about 4.5 km s-1, and the averages of residuals after sky subtraction are about 3% for sky emission lines and 3% for the continuum region. The relative sky subtraction residuals vary with moonlight background brightness, and can reach as low as 1.5% for regions that have sky emission lines during a dark night. Tests on F stars with both similar sky emission line strength and similar object continuum intensity show that the sky emission line residual of LAMOST is smaller than that of the SDSS survey.

关键词： techniques: spectroscopic -- methods data analysis -- instrumentation spectrographs