A5103168071- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Astronomical Observations and Instrumentation
- Topic Modeling
- Natural Language Processing Techniques
- Gamma-ray bursts and supernovae
- Text Readability and Simplification
Sun Yat-sen University
2020-2021
Chinese Academy of Sciences
2012-2018
National Astronomical Observatories
2017-2018
Pontificia Universidad Católica de Chile
2017
Shanghai Astronomical Observatory
2011-2014
University of Chinese Academy of Sciences
2012-2014
Kavli Institute for Theoretical Sciences
2011
Peking University
2011
We present the age–velocity dispersion relation (AVR) in three dimensions solar neighbourhood using 3564 commonly observed sub-giant/red giant branch stars selected from The Large Sky Area Multi-Object Fiber Spectroscopic Telescope, which gives age and radial velocity, Gaia, measures distance proper motion. are separated into metal-poor ([Fe/H] < −0.2 dex metal-rich > dex) groups, so that mostly α-poor, while group contributed by α-enhanced stars. Thus, old likely belong to chemically...
Since September 2018, LAMOST starts a new 5-year medium-resolution spectroscopic survey (MRS) using bright/gray nights. We present the scientific goals of LAMOST-MRS and propose near optimistic strategy survey. A complete footprint is also provided. Not only regular survey, but time-domain being conducted since 2018 will be end in 2023. According to detailed plan, we expect that can observe about 2 million stellar spectra with ~7500 limiting magnitude around G=15 mag. Moreover, it provide...
Large language models (LLMs) have pushed the limits of natural understanding and exhibited excellent problem-solving ability. Despite great success, most existing open-source LLMs (e.g., LLaMA-2) are still far away from satisfactory for solving mathematical problem due to complex reasoning procedures. To bridge this gap, we propose MetaMath, a fine-tuned model that specializes in reasoning. Specifically, start by bootstrapping questions rewriting question multiple perspectives without extra...
Abstract The binary properties of open clusters place crucial constraints on star formation theory and clusters’ dynamical evolution. We develop a comprehensive approach that models the color–magnitude diagram (CMD) cluster members as mixture single stars photometric unresolved binaries. This method enables us to infer properties, including fraction f b mass ratio distribution index γ q when power law is assumed, with high accuracy precision, which was unfeasible in conventional methods....
We describe the target selection algorithm for low latitude disk portion of LAMOST Pilot Survey, which aims to test systems in preparation spectroscopic survey. use PPMXL astrometric catalog, provides positions, proper motions, B/R/I magnitudes (mostly) from USNO-B and J/H/Ks Two Micron All Sky Survey (2MASS) as well. chose eight plates along Galactic plane, region 0° < α 67° 42° δ 59°, cover 22 known open clusters with a range ages. Adjacent may have some small overlapping area. Each plate...
Abstract We derive stellar population parameters for a representative sample of ultracompact dwarfs (UCDs) and large massive globular clusters (GCs) with masses ≳ 10 6 M ⊙ in the central galaxy M87 Virgo cluster, based on model fitting to Lick-index measurements from both literature new observations. After necessary spectral stacking relatively faint objects our initial 40 UCDs 118 GCs, we obtain 30 sets 80 GCs. The have ages 8 Gyr [ α /Fe] ≃ 0.4 dex, agreement previous studies smaller...
Interesting chemically peculiar field stars may reflect their stellar evolution history and possible origin in a different environment from where they are found now, which is one of the most important research fields Galactic archaeology. To explore this further, we have used CN-CH bands around 4000 A to identify N-rich metal-poor LAMOST DR3. Here expand our star sample ~100 DR5, 53 them newly work. We investigate light elements common between APOGEE DR14. While Mg, Al, Si abundances...
We investigate the evolution of young star clusters using N-body simulations. confirm that subvirial and fractal-structured will dynamically mass segregate on a short timescale (within 0.5 Myr). adopt modified minimum-spanning-tree method to measure degree segregation, demonstrating stars escaping from cluster's potential are important for temporal dependence segregation in cluster. The form initial velocity distribution also affect segregation. If it depends radius, outer parts cluster...
We use samples of local main-sequence stars to show that the radial gradient [Fe/H] in thin disk Milky Way decreases with mean effective stellar temperature. Many these are visiting solar neighborhood from inner and outer Galaxy. angular momentum each star about Galactic center determine guiding radius eliminate effects epicyclic motion, which would otherwise blur estimated gradients. interpret temperature as a proxy for age, conclude decreasing is consistent predictions mixing due transient...
Since the discovery of chemically peculiar stars in globular clusters last century, study multiple populations has become increasingly important, given that chemical inhomogeneity is found almost all clusters. Despite various proposed theories attempting to explain this phenomenon, fitting observational evidence with one single theory remains notoriously difficult and currently unsuccessful. In order improve existing models motivate new ones, we are observing at critical conditions, e.g.,...
We compare the existent methods, including minimum spanning tree based method and local stellar density method, in measuring mass segregation of star clusters. find that reflects more compactness, which represents global spatial distribution massive stars, while crowdedness, provides gravitational potential information. It is suggested to measure simultaneously. also develop a hybrid takes both aspects into account. This balances sense predominant one either caused by dynamical evolution or...
Abstract We measure chemical abundances for over 20 elements of 15 N-rich field stars with high-resolution ( R ∼ 30,000) optical spectra. find that Na, Mg, Al, Si, and Ca our are mostly consistent those from globular clusters (GCs). Seven estimated to have [Al/Fe ] > 0.5, which is not found in most GC “first generation” stars. On the other hand, α element (especially Ti) could show distinguishable differences between situ accreted discover one interesting star, consistently low [Mg/Fe],...
We report the parallax and proper motion of five L dwarfs obtained with observations from robotic Liverpool Telescope. Our derived motions are consistent published values have considerably smaller errors. Based on our spectral type versus absolute magnitude diagram, we do not find any evidence for binaries among sample, or, at least no comparable mass binaries. Their space velocities locate them within thin disk based model comparisons they solar-like abundances. For all objects, effective...
Abstract We use samples of local main-sequence stars to show that the radial gradient [Fe/H] in thin disk Milky Way decreases with mean effective stellar temperature. angular momentum each star about Galactic center eliminate effects epicyclic motion, which would otherwise blur estimated gradients. temperatures as a proxy for age, and conclude decreasing is consistent predictions mixing due transient spiral patterns. find some evidence trend increasing age breaks constant whose life-times...
Abstract In this paper, we present our recent work on the evolution of abundance gradients along Milky Way disk based Geneva Copenhagen Survey (GCS) and Radial Velocity Experiment (RAVE) data. We will also discuss role LAMOST survey in clarifying properties metallicity breaks observed through open clusters young tracers disk. It is believed that Galactic forms inside-out, which stellar population at increasing radii younger more metal poor. This picture consistent with most Chemical...