Two Li-rich candidates,TYC 1338-1410-1 and TYC 2825-596-1,were observed by the new high-resolution echelle spectrograph,LAMOST/HRS.Based on their high-resolution and high-signal-tonoise ratio(SNR)spectra,we derived st...Two Li-rich candidates,TYC 1338-1410-1 and TYC 2825-596-1,were observed by the new high-resolution echelle spectrograph,LAMOST/HRS.Based on their high-resolution and high-signal-tonoise ratio(SNR)spectra,we derived stellar parameters and abundances of 14 important elements for the two candidates.The stellar parameters and lithium abundances indicate that they are Li-rich K-type giants,and having A(Li)NLTE and 2.91 dex,respectively.Our analysis suggests that TYC 1338-1410-1 is probably a red giant branch(RGB)star at the bump stage,while TYC 2825-596-1 is most likely to be a core helium-burning red clump(RC)star.The line profiles of both spectra indicate that the two Li-rich giants are slow rotators and do not show infrared(IR)excess.We conclude that engulfment is not the lithium enrichment mechanism for either star.The enriched lithium of TYC 1338-1410-1 could be created via the Cameron-Fowler mechanism,while the lithium excess in TYC 2825-596-1 could be associated with either non-canonical mixing processes or He-flash.展开更多
We describe the current plans for a spectroscopic survey of millions of stars in the Milky Way galaxy using the Guo Shou Jing Telescope (GSJT, formerly calledthe Large sky Area Multi-Object fiber Spectroscopic Telesc...We describe the current plans for a spectroscopic survey of millions of stars in the Milky Way galaxy using the Guo Shou Jing Telescope (GSJT, formerly calledthe Large sky Area Multi-Object fiber Spectroscopic Telescope -- LAMOST). The survey will obtain spectra for 2.5 million stars brighter than r 〈 19 during dark/grey time, and 5 million stars brighter than r 〈 17 or J 〈 16 on nights that are moonlit or have low transparency. The survey will begin in the fall of 2012, and will run for at least four years. The telescope's design constrains the optimal declination range for observations to 10~ 〈 di 〈 50~, and site conditions lead to an emphasis on stars in the direction of the Galactic anticenter. The survey is divided into three parts with different target selection strategies: disk, anticenter, and spheroid. The resulting dataset will be used to study the merger history of the Milky Way, the substructure and evolution of the disks, the nature of the first generation of stars through identification of the lowest metallicity stars, and star formation through study of open clusters and OB associations. Detailed design of the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) survey will be completed in summer 2012, after a review of the results of the pilot survey.展开更多
The weather at the Xinglong Observing Station, where the Guo Shou Jing Telescope (GSJT) is located, is strongly affected by the monsoon climate in north- east China. The LAMOST survey strategy is constrained by thes...The weather at the Xinglong Observing Station, where the Guo Shou Jing Telescope (GSJT) is located, is strongly affected by the monsoon climate in north- east China. The LAMOST survey strategy is constrained by these weather patterns. We present statistics on observing hours from 2004 to 2007, and the sky brightness, seeing, and sky transparency from 1995 to 2011 at the site. We investigate effects of the site conditions on the survey plan. Operable hours each month show a strong cor- relation with season: on average there are eight operable hours per night available in December, but only one-two hours in July and August. The seeing and the sky trans- parency also vary with season. Although the seeing is worse in windy winters, and the atmospheric extinction is worse in the spring and summer, the site is adequate for the proposed scientific program of the LAMOST survey. With a Monte Carlo simulation using historical data on the site condition, we find that the available observation hours constrain the survey footprint from 22h to 16h in right ascension; the sky brightness allows LAMOST to obtain a limiting magnitude of V = 19.5 mag with S/N= 10.展开更多
We describe a general target selection algorithm that is applicable to any survey in which the number of available candidates is much larger than the number of objects to be observed. This routine aims to achieve a ba...We describe a general target selection algorithm that is applicable to any survey in which the number of available candidates is much larger than the number of objects to be observed. This routine aims to achieve a balance between a smoothly- varying, well-understood selection function and the desire to preferentially select cer- tain types of targets. Some target-selection examples are shown that illustrate differentpossibilities of emphasis functions. Although it is generally applicable, the algorithm was developed specifically for the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) survey that will be carried out using the Chinese Guo Shou Jing Telescope. In particular, this algorithm was designed for the portion of LEGUE targeting the Galactic halo, in which we attempt to balance a variety of science goals that require stars at fainter magnitudes than can be completely sampled by LAMOST. This algorithm has been implemented for the halo portion of the LAMOST pilot sur- vey, which began in October 2011.展开更多
We report the discovery of two r-process-enhanced stars with [Fe/H]>-0.6 dex selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) survey.Three candidate stars have been selected from ...We report the discovery of two r-process-enhanced stars with [Fe/H]>-0.6 dex selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) survey.Three candidate stars have been selected from the LAMOST medium-resolution(R~ 7500) spectroscopic survey,and the follo wed-up high signal-to-noise ratio and high-resolution(R~31,500) spectra are obtained with the ARC Echelle Spectrograph mounted on the3.5 m telescope at the Apache Point Observatory,which allow us for the determination of stellar atmospheric parameters and abundances of 20 elements.Among these three r-process-enhanced candidate stars,TYC 1710-933-1 and TYC 2858-372-1 have [Eu/Fe] higher than 0.3 dex and [Ba/Eu] lower than 0.0 dex,thus,can be identified as new r-process-enhanced objects.TYC 2858-372-1 shows similar r+s-process pattern to the Sun.TYC 1710-933-1 presents enhancement of the r-process elements of Nd and Eu.Our work indicates that the enrichment mechanisms of the heavy neutron-capture elements are complicated for metal-rich stars.展开更多
We describe the target selection algorithm for the low latitude disk por- tion of the LAMOST Pilot Survey, which aims to test systems in preparation for the LAMOST spectroscopic survey. We use the PPMXL astrometric ca...We describe the target selection algorithm for the low latitude disk por- tion of the LAMOST Pilot Survey, which aims to test systems in preparation for the LAMOST spectroscopic survey. We use the PPMXL astrometric catalog, which provides positions, proper motions, B/R/I magnitudes (mostly) from USNO-B and d/H/Ks from the Two Micron All Sky Survey (2MASS) as well. We chose eight plates along the Galactic plane, in the region 0° 〈 α° 〈 67° and 42° 〈 δ 〈 59°, which cover 22 known open clusters with a range of ages. Adjacent plates may have some small overlapping area. Each plate covers an area of 2.5° in radius, with its cen- tral star (for the Shack-Hartmann guider) brighter than 8th magnitude. For each plate, we create an input catalog in the magnitude range 11.3 〈 Imag 〈 16.3 and Bmag available from PPMXL. The stars are selected to satisfy the requirements of the fiber positioning system and have a uniform distribution in the I vs. B - I color-magnitude diagram. Our final input catalog consists of 12 000 objects on each of eight plates that are observable during the winter observing season from the Xinglong Station of the National Astronomical Observatory of China.展开更多
We describe the footprint and input catalog for bright nights in the LAMOST Pilot Survey, which began in October 2011. Targets are selected from two stripes in the north and south Galactic Cap regions, centered at δ ...We describe the footprint and input catalog for bright nights in the LAMOST Pilot Survey, which began in October 2011. Targets are selected from two stripes in the north and south Galactic Cap regions, centered at δ = 29°, with 10° width in declination, covering right ascensions of 135° to 290° and -30° to 30° re- spectively. We selected spectroscopic targets from a combination of the SDSS and 2MASS point source catalogs. The catalog of stars defining the field centers (as re- quired by the Shack-Hartmann wavefront sensor at the center of the LAMOST field) consists of all V 〈 8m stars from the Hipparcos catalog. We employ a statistical selection algorithm that assigns priorities to targets based on their positions in mul- tidimensional color/magnitude space. This scheme overemphasizes rare objects and de-emphasizes more populated regions of magnitude and color phase space, while en- suring a smooth, well-understood selection function. A demonstration of plate design is presented based on the Shack-Hartmann star catalog and an input catalog that was generated by our target selection routines.展开更多
We outline the design of the dark nights portion of the LAMOST Pilot Survey, which began observations in 2011 October. In particular, we focus on Milky Way stellar candidates that are targeted for the LEGUE (LAMOST E...We outline the design of the dark nights portion of the LAMOST Pilot Survey, which began observations in 2011 October. In particular, we focus on Milky Way stellar candidates that are targeted for the LEGUE (LAMOST Experiment for Galactic Understanding and Exploration) survey. We discuss the regions of sky in which spectroscopic candidates were selected, and the motivations for selecting each of these sky areas. Some limitations due to the unique design of the telescope are discussed, including the requirement that a bright (V 〈 8) star be placed at the center of each plate for wavefront sensing and active optics corrections. The target selection categories and scientific goals motivating them are briefly discussed, followed by a detailed overview of how these selection functions were implemented. We illustrate the difference between the overall input catalog - Sloan Digital Sky Survey (SDSS) photometry - and the final targets selected for LAMOST observations.展开更多
基金the National Key R&D Program of China(No.2019YFA0405502)the Key Research Program of the Chinese Academy of Sciences under grant No.XDPB09-02+8 种基金the National Natural Science Foundation of China(Grant Nos.11973052,11833006,11473033 and 11603037)the International partnership program’s Key foreign cooperation project,Bureau of International Cooperation,Chinese Academy of Sciences(No.114A32KYSB20160049)supported by the Astronomical Big Data Joint Research Center,co-founded by the National Astronomical Observatories,Chinese Academy of Sciences and Alibaba Cloudpartially supported by the Open Project Program of the Key Laboratory of Optical Astronomy,National Astronomical Observatories,Chinese Academy of Sciencesthe financial support from China Scholarship Council(CSC,No.201604910642)for his study at New Mexico State University in the United States of Americathe supports from Youth Innovation Promotion Association,Chinese Academy of SciencesGuo Shou Jing Telescope(the Large Sky Area Multi-Object Fiber Spectroscopic Telescope LAMOST)is a National Major Scientific Project built by the Chinese Academy of Sciences.Funding for the project has been provided by the National Development and Reform Commissionthe NASA/IPAC Infrared Science Archive,which is funded by the National Aeronautics and Space Administrationthe Wide-field Infrared Survey Explorer,which is a joint project of the University of California,Los Angeles,and the Jet Propulsion Laboratory/California Institute of Technology,funded by the National Aeronautics and Space Administration。
文摘Two Li-rich candidates,TYC 1338-1410-1 and TYC 2825-596-1,were observed by the new high-resolution echelle spectrograph,LAMOST/HRS.Based on their high-resolution and high-signal-tonoise ratio(SNR)spectra,we derived stellar parameters and abundances of 14 important elements for the two candidates.The stellar parameters and lithium abundances indicate that they are Li-rich K-type giants,and having A(Li)NLTE and 2.91 dex,respectively.Our analysis suggests that TYC 1338-1410-1 is probably a red giant branch(RGB)star at the bump stage,while TYC 2825-596-1 is most likely to be a core helium-burning red clump(RC)star.The line profiles of both spectra indicate that the two Li-rich giants are slow rotators and do not show infrared(IR)excess.We conclude that engulfment is not the lithium enrichment mechanism for either star.The enriched lithium of TYC 1338-1410-1 could be created via the Cameron-Fowler mechanism,while the lithium excess in TYC 2825-596-1 could be associated with either non-canonical mixing processes or He-flash.
基金partially supported by the National Natural Science Foundation of China (Grant Nos. 10573022, 10973015, 11061120454and 11243003)the US National Science Foundation through grant AST-09-37523
文摘We describe the current plans for a spectroscopic survey of millions of stars in the Milky Way galaxy using the Guo Shou Jing Telescope (GSJT, formerly calledthe Large sky Area Multi-Object fiber Spectroscopic Telescope -- LAMOST). The survey will obtain spectra for 2.5 million stars brighter than r 〈 19 during dark/grey time, and 5 million stars brighter than r 〈 17 or J 〈 16 on nights that are moonlit or have low transparency. The survey will begin in the fall of 2012, and will run for at least four years. The telescope's design constrains the optimal declination range for observations to 10~ 〈 di 〈 50~, and site conditions lead to an emphasis on stars in the direction of the Galactic anticenter. The survey is divided into three parts with different target selection strategies: disk, anticenter, and spheroid. The resulting dataset will be used to study the merger history of the Milky Way, the substructure and evolution of the disks, the nature of the first generation of stars through identification of the lowest metallicity stars, and star formation through study of open clusters and OB associations. Detailed design of the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) survey will be completed in summer 2012, after a review of the results of the pilot survey.
基金partially supported by the Chinese Academy of Sciences through grant GJHZ 200812the National Natural Science Foundation of China (Grant Nos. 11243003, 10573022,10973015 and 11061120454)the US National Science Foundation, through grant AST-09-37523
文摘The weather at the Xinglong Observing Station, where the Guo Shou Jing Telescope (GSJT) is located, is strongly affected by the monsoon climate in north- east China. The LAMOST survey strategy is constrained by these weather patterns. We present statistics on observing hours from 2004 to 2007, and the sky brightness, seeing, and sky transparency from 1995 to 2011 at the site. We investigate effects of the site conditions on the survey plan. Operable hours each month show a strong cor- relation with season: on average there are eight operable hours per night available in December, but only one-two hours in July and August. The seeing and the sky trans- parency also vary with season. Although the seeing is worse in windy winters, and the atmospheric extinction is worse in the spring and summer, the site is adequate for the proposed scientific program of the LAMOST survey. With a Monte Carlo simulation using historical data on the site condition, we find that the available observation hours constrain the survey footprint from 22h to 16h in right ascension; the sky brightness allows LAMOST to obtain a limiting magnitude of V = 19.5 mag with S/N= 10.
基金supported by the US National Science Foundation, through grant AST-09-37523the National Natural Science Foundation of China (Grant Nos. 10573022, 10973015 and 11061120454)+1 种基金the Chinese Academy of Sciences through grant GJHZ 200812S. L. is supported by the US National Science Foundation grant AST-09-08419
文摘We describe a general target selection algorithm that is applicable to any survey in which the number of available candidates is much larger than the number of objects to be observed. This routine aims to achieve a balance between a smoothly- varying, well-understood selection function and the desire to preferentially select cer- tain types of targets. Some target-selection examples are shown that illustrate differentpossibilities of emphasis functions. Although it is generally applicable, the algorithm was developed specifically for the LAMOST Experiment for Galactic Understanding and Exploration (LEGUE) survey that will be carried out using the Chinese Guo Shou Jing Telescope. In particular, this algorithm was designed for the portion of LEGUE targeting the Galactic halo, in which we attempt to balance a variety of science goals that require stars at fainter magnitudes than can be completely sampled by LAMOST. This algorithm has been implemented for the halo portion of the LAMOST pilot sur- vey, which began in October 2011.
基金supported by the National Key R&D Program of China No. 2019YFA0405502the National Natural Science Foundation of China under grant Nos. 12090040, 12090044, 11833006, 12022304, 11973052, 11973042 and U2031144+4 种基金the science research grants from the China Manned Space Project with NO.CMS-CSST-2021B05the supports from Youth Innovation Promotion Association (id. 2019060), Chinese Academy of SciencesPhysics Frontier Center/JINA Center for the Evolution of the Element (JINA-CEE), awarded by the US National Science Foundationpartially supported by the Open Project Program of the Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of SciencesGuo Shou Jing Telescope (the Large Sky Area MultiObject Fiber Spectroscopic Telescope, LAMOST) is a National Major Scientific Project built by the Chinese Academy of Sciences. Funding for the project has been provided by the National Development and Reform Commission。
文摘We report the discovery of two r-process-enhanced stars with [Fe/H]>-0.6 dex selected from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST) survey.Three candidate stars have been selected from the LAMOST medium-resolution(R~ 7500) spectroscopic survey,and the follo wed-up high signal-to-noise ratio and high-resolution(R~31,500) spectra are obtained with the ARC Echelle Spectrograph mounted on the3.5 m telescope at the Apache Point Observatory,which allow us for the determination of stellar atmospheric parameters and abundances of 20 elements.Among these three r-process-enhanced candidate stars,TYC 1710-933-1 and TYC 2858-372-1 have [Eu/Fe] higher than 0.3 dex and [Ba/Eu] lower than 0.0 dex,thus,can be identified as new r-process-enhanced objects.TYC 2858-372-1 shows similar r+s-process pattern to the Sun.TYC 1710-933-1 presents enhancement of the r-process elements of Nd and Eu.Our work indicates that the enrichment mechanisms of the heavy neutron-capture elements are complicated for metal-rich stars.
基金funded by the National Natural Science Foundation of China (Grant Nos. 11173044(PI: Hou), 11073038 (PI: Chen), 10573022, 10973015 and 11061120454 (PI: Deng))the Key Project No.10833005 (PI: Hou)+2 种基金the Group Innovation Project No.11121062the US National Science Foundation grant AST 09-37523Chinese Academy of Sciences is acknowledged for providing initial support from grant number GJHZ 200812
文摘We describe the target selection algorithm for the low latitude disk por- tion of the LAMOST Pilot Survey, which aims to test systems in preparation for the LAMOST spectroscopic survey. We use the PPMXL astrometric catalog, which provides positions, proper motions, B/R/I magnitudes (mostly) from USNO-B and d/H/Ks from the Two Micron All Sky Survey (2MASS) as well. We chose eight plates along the Galactic plane, in the region 0° 〈 α° 〈 67° and 42° 〈 δ 〈 59°, which cover 22 known open clusters with a range of ages. Adjacent plates may have some small overlapping area. Each plate covers an area of 2.5° in radius, with its cen- tral star (for the Shack-Hartmann guider) brighter than 8th magnitude. For each plate, we create an input catalog in the magnitude range 11.3 〈 Imag 〈 16.3 and Bmag available from PPMXL. The stars are selected to satisfy the requirements of the fiber positioning system and have a uniform distribution in the I vs. B - I color-magnitude diagram. Our final input catalog consists of 12 000 objects on each of eight plates that are observable during the winter observing season from the Xinglong Station of the National Astronomical Observatory of China.
基金partially supported by the National Natural Science Foundation of China (Grant Nos. 10573022, 10973015 and 11061120454)the Chinese Academy of Sciences through grant GJHZ 20081the US National Science Foundation through grant AST-09-37523
文摘We describe the footprint and input catalog for bright nights in the LAMOST Pilot Survey, which began in October 2011. Targets are selected from two stripes in the north and south Galactic Cap regions, centered at δ = 29°, with 10° width in declination, covering right ascensions of 135° to 290° and -30° to 30° re- spectively. We selected spectroscopic targets from a combination of the SDSS and 2MASS point source catalogs. The catalog of stars defining the field centers (as re- quired by the Shack-Hartmann wavefront sensor at the center of the LAMOST field) consists of all V 〈 8m stars from the Hipparcos catalog. We employ a statistical selection algorithm that assigns priorities to targets based on their positions in mul- tidimensional color/magnitude space. This scheme overemphasizes rare objects and de-emphasizes more populated regions of magnitude and color phase space, while en- suring a smooth, well-understood selection function. A demonstration of plate design is presented based on the Shack-Hartmann star catalog and an input catalog that was generated by our target selection routines.
基金partially supported by the National Natural Science Foundation of China(Grant Nos. 10573022, 10973015 and 11061120454)the US National Science Foundation through AST grant 09-37523The Chinese Academy of Sciences is acknowledged for providing the initial support through grant GJHZ 200812
文摘We outline the design of the dark nights portion of the LAMOST Pilot Survey, which began observations in 2011 October. In particular, we focus on Milky Way stellar candidates that are targeted for the LEGUE (LAMOST Experiment for Galactic Understanding and Exploration) survey. We discuss the regions of sky in which spectroscopic candidates were selected, and the motivations for selecting each of these sky areas. Some limitations due to the unique design of the telescope are discussed, including the requirement that a bright (V 〈 8) star be placed at the center of each plate for wavefront sensing and active optics corrections. The target selection categories and scientific goals motivating them are briefly discussed, followed by a detailed overview of how these selection functions were implemented. We illustrate the difference between the overall input catalog - Sloan Digital Sky Survey (SDSS) photometry - and the final targets selected for LAMOST observations.