A5053709811- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Astronomical Observations and Instrumentation
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Solar and Space Plasma Dynamics
- Adaptive optics and wavefront sensing
- High-pressure geophysics and materials
- Luminescence and Fluorescent Materials
- Scientific Research and Discoveries
- Synthesis and Properties of Aromatic Compounds
- Nuclear physics research studies
- Covalent Organic Framework Applications
National Astronomical Observatories
2014-2024
Chinese Academy of Sciences
2014-2024
Beijing National Laboratory for Molecular Sciences
2024
Institute of Chemistry
2024
University of Chinese Academy of Sciences
2008-2024
For the first time, we present an extensive study of stars with individual non-local thermodynamic equilibrium (NLTE) abundances for 17 chemical elements from Li to Eu in a sample uniformly distributed over $-2.62 \le$ [Fe/H] $\le +0.24$ metallicity range that is suitable Galactic evolution research. The star has been kinematically selected trace thin and thick disks halo. We find new improve earlier results as follows. (i) element-to-iron ratios Mg, Si, Ca, Ti form MP plateau at similar...
We present atmospheric parameters for 51 nearby FG dwarfs uniformly distributed over the -2.60 < [Fe/H] +0.20 metallicity range that is suitable Galactic chemical evolution research. Lines of iron, Fe I and II, were used to derive a homogeneous set effective temperatures, surface gravities, iron abundances, microturbulence velocities. high-resolution (R>60000) Shane/Hamilton CFHT/ESPaDOnS observed spectra non-local thermodynamic equilibrium (NLTE) line formation II in classical 1D model...
Abstract We present the result of a search for very metal-poor (VMP, <?CDATA ${\rm{[Fe/H]}}\lt -2.0$?> ) stars in Milky Way based on low-resolution spectra from Large sky Area Multi-Object fiber Spectroscopic Telescope (LAMOST) DR3, significantly enlarging current candidate sample these low-metallicity objects. The selection procedure results 10,008 VMP covering large area Northern Hemisphere, and includes over 6800 targets brighter than V ∼ 16. This LAMOST DR3 provides largest number...
Abstract In this paper, we propose a new method to estimate stellar atmospheric parameters with photometric data, which is based on principal component analysis (PCA) and light gradient boosting machine (LightGBM) algorithms. We first use PCA transform all band data ( u , v g r i z ) then utilize LightGBM parameters. The experimental results show that the root mean square errors of for estimating effective temperature, surface gravity, metallicity are 90 K, 0.40 dex, 0.20 respectively....
The lithium abundances for 378 G/K giants are derived with non-LTE correction considered. Among these, there 23 stars that host planetary systems. abundance is investigated, as a function of metallicity, effective temperature, and rotational velocity, well the impact giant planet on giants. results show metallicity temperature. has no correlation velocity at vsini $<$ 10 km s$^{-1}$. Giants planets present lower slow (vsini 4 s$^{-1}$). Our sample includes three Li-rich giants, 36 Li-normal...
Abstract The Stellar Abundances and Galactic Evolution Survey (SAGES) of the northern sky is a specifically designed multiband photometric survey aiming to provide reliable stellar parameters with accuracy comparable those from low-resolution optical spectra. It was carried out 2.3 m Bok telescope Steward Observatory three other telescopes. observations in u s v passband produced over 36,092 frames images total, covering area ∼9960 deg 2 . median completenesses all observing fields for two...
Abstract We present precise photometric estimates of stellar parameters, including effective temperature, metallicity, luminosity classification, distance, and age, for nearly 26 million stars using the methodology developed in first paper this series, based on colors from Stellar Abundances Galactic Evolution Survey (SAGES) Data Release 1 Gaia Early 3. The optimal design stellar-parameter sensitive uv filters by SAGES has enabled us to determine photometric-metallicity down −3.5, similar...
Abstract Photometric stellar surveys now cover a large fraction of the sky, probe to fainter magnitudes than large-scale spectroscopic surveys, and are relatively free from target selection biases often associated with such studies. Photometric-metallicity estimates that include narrow/medium-band filters can achieve comparable accuracy precision existing low-resolution as Sloan Digital Sky Survey/SEGUE LAMOST. Here we report on an effort identify likely members Galactic disk system among...
Stellar parameters for large samples of stars play a crucial role in constraining the nature and stellar populations Galaxy. An increasing number medium-band photometric surveys are presently used estimating parameters. In this study, we present machine-learning approach to derive estimates parameters, including [Fe/H], logg, Teff, based on combination broad-band observations. Our analysis employs data primarily sourced from SAGE Survey , which aims observe much Northern Hemisphere. We...
Abstract Stellar parameters for large samples of stars play a crucial role in constraining the nature and stellar populations Galaxy. An increasing number medium-band photometric surveys are presently used estimating parameters. In this study, we present machine learning approach to derive estimates parameters, including [Fe/H], log g , T eff based on combination broadband observations. Our analysis employs data primarily sourced from Abundances Galactic Evolution Survey (SAGES), which aims...
Context. Cool star model atmospheres are a common tool for the investigation of stellar masses, ages and elemental abundance composition. Theoretical atmospheric models strongly depend on atomic data used when calculating them. Aims. We present changes in flux temperature stratification changing from iron computed by R.L. Kurucz mid 90s to 2009 computations. Methods. MAFAGS-OS opacity sampling were recomputed with as implemented VALD database Ryabchikova. Temperature emergent distribution...
<i>Context. <i/>Cool star model atmospheres are a common tool for the investigation of stellar masses, ages and elemental abundance composition. Theoretical atmospheric models strongly depend on atomic data used when calculating them.<i>Aims. <i/>We present changes in flux temperature stratification changing from iron computed by R.L. Kurucz mid 90s to 2009 computations.<i>Methods. <i/>MAFAGS-OS opacity sampling were recomputed with as implemented VALD database Ryabchikova. Temperature...
To investigate a huge sample of data related to the Stellar Abundance and Galactic Evolution (SAGE) survey in more detail, we are performing northern sky photometric named SAGES with SAGE system. This system consists eight filters: Strӧmgren-u, SAGE-v, SDSS g, r, i, DDO-51, Hαwide Hαnarrow, including three Sloan broadband filters, intermediate-band two narrow-band filters one newly-designed filter. covers ∼12 000 square degrees δ > −5°, excluding disk (|b| < 10°) area 12 h RA 18 h. The...
We have determined beryllium (Be) abundances for 25 metal-poor stars based on the high-resolution and high signal-to-noise ratio spectra from Very Large Telescope/Ultraviolet Visual Echelle Spectrograph data base. Our results confirm that Be increase with Fe, supporting global enrichment of in Galaxy. Oxygen [O i] forbidden line imply a linear relation slope close to one versus O trend, which indicates is probably produced primary process. Some strong evidence found intrinsic dispersion at...
We have obtained a sample of ∼22,000 red giant branch (RGB) stars based on stellar parameters, provided by the ninth data release Sloan Digital Sky Survey, and CH(G)/MgH indices, measured from included spectra. The Galactic rest-frame velocity Vgsr versus longitude for shows existence several groups globular clusters known streams. Excluding these substructures, ∼16,000 RGB general field is used to investigate properties thick disk, inner halo, outer halo our Galaxy. metallicity rotational...
We present chromospheric activity index SHK measurements for 119 995 F, G and K stars with high signal-to-noise ratio (S/N > 80) spectra, extracted from LAMOST DR1 in SDSS g band. The δS each of these is calculated by the difference between its value baseline determined very inactive stars. effect metallicity on measurement varies stellar Teff. No evident Vaughan-Preston gap appears our sample. relation vertical distance Galactic plane Teff < 5500 K. Stars higher tend to be closer plane. Two...
We have used high-resolution, high signal-to-noise ratio infrared spectra from the Subaru Telescope atop Mauna Kea. Line formation calculations of Si i lines in atmospheres nearby stars are presented. All abundance results [Si/Fe] derived local thermodynamic equilibrium (LTE) and NLTE statistical spectrum synthesis methods. found that effects for important even metal-rich (>0.1 dex), may depend on surface gravities. A good agreement silicon abundances between optical is obtained when...
We have cross-matched the LAMOST DR2 with WISE, 2MASS and PPMXL catalogs obtained a sample of 64 819 FGK metal-poordwarfs [Fe/H] < −0.7, distances within 2 kpc from Sun reliable kinematics (space velocities, angular momenta eccentricities). With detection strategy for halo streams provided by Klement et al, nine significant "phase-space overdensities" stars on very similar orbits are identified this sample. Among these overdensities, three were previously known six new stream candidates. The...
Sky surveys represent one of the most important efforts to improve developments in astrophysics, especially when using new photometric bands. We are performing Stellar Abundance and Galactic Evolution (SAGE) survey with a self-designed SAGE system, which is composed eight The project mainly aims study stellar atmospheric parameters ∼0.5 billion stars ∼12 000 deg2 northern sky, focuses on astronomy, as well some aspects extragalactic astronomy. This work introduces detailed data reduction...
Abstract We report the discovery of a new stream (dubbed as Yangtze) detected in Gaia Data Release 3. The is at heliocentric distance ∼9.12 kpc and spans nearly 27° by 1.°9 on sky. color–magnitude diagram Yangtze indicates stellar population age ∼11 Gyr [M/H] ∼ −0.7 dex. It has number density about 5.5 stars deg −2 along with surface brightness Σ G ≃ 34.9 mag arcsec . dynamics metallicity estimate suggest that may be closely related to Palomar 1 Anticenter Stream.
Most of the previous studies on beryllium abundances in metal-poor stars have taken different Galactic populations as a whole when investigating production and evolution Be. In this Letter, we report detection systematic differences [α/H]–A(Be) relationships between low- high-α which were identified by works. We remind that one should be more careful Be with sample comprising populations, because such mixed may lead to inaccurate Be–Fe/Be–O relationships.
We analyze the kinematics of thick disk and halo stars observed by Large sky Area Multi-Object Fiber Spectroscopic Telescope. have constructed a sample 7,993 F, G K nearby main-sequence (\textit{d} $<$ 2 kpc) with estimates position (x, y, z) space velocity ($U$, $V$, $W$) based on color proper motion from SDSS DR9 catalog. Three `phase-space overdensities' are identified in [\textit{V}, $\sqrt{U^{2}+2V^{2}}$] significance levels $\sigma$ $>$ 3. %[L$_{Z}$, eccentricity], [L$_{Z}$,...
We present distance determinations for a large and clean sample of red giant branch stars selected from the ninth data release Sloan Digital Sky Survey. The distances are calculated based on both observational cluster fiducials theoretical isochrones. Distributions two methods very similar with peaks at about 10 kpc tails extending to more than 70 kpc. find that agree well majority stars; though, average, isochrones 10% higher those fiducials. test accuracy our using 332 Galactic globular...
The non-local thermodynamic equilibrium (NLTE) line formation of neutral boron in the atmospheres cool stars are investigated. Our results confirm that NLTE effects for B I resonance lines, which due to a combination overionization and optical pumping effects, most important hot, metalpoor, low-gravity stars; however, amplitude departures from LTE found by this work smaller than previous studies. In addition, our calculation shows will get closer if strength collisions with hydrogen...
Photometric stellar surveys now cover a large fraction of the sky, probe to fainter magnitudes than large-scale spectroscopic surveys, and are relatively free from target-selection biases often associated with such studies. Photometric-metallicity estimates that include narrow/medium-band filters can achieve comparable accuracy precision existing low-resolution as SDSS/SEGUE LAMOST. Here we report on an effort identify likely members Galactic disk system among very metal-poor (VMP; [Fe/H]...