Abundance Estimates for 16 Elements in 6 Million Stars from LAMOST DR5 Low-Resolution Spectra

Xiang, Maosheng; Ting, Yuan-Sen; Rix, Hans─Walter; Sandford, Nathan R.; Buder, Sven; Lind, Karin; Liu, Xiaowei; Shi, Jianrong; Zhang, Huawei

doi:10.3847/1538-4365/ab5364

Cited by 198 publications

(263 citation statements)

References 96 publications

(117 reference statements)

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“…However, the spectral energy distribution (SED) is best fit with an effective temperature of 6000 K. To exclude identification issues, we double checked the identifications of the LAMOST spectrum and the photometry employed for the SED fitting; no misidentifications were detected. In the literature, we also find widely different effective temperature estimates for this star: 5325 K (Ammons et al 2006), 6210 K (Stassun et al 2019), 6785 K (Bai et al 2019), 7950 K (Xiang et al 2019), and 9500 K (Bai et al 2018). The wide range of different temperature values points towards a spectroscopic binary system observed at different phases.…”

Section: Colour-magnitude Diagrammentioning

confidence: 59%

New mercury-manganese stars and candidates from LAMOST DR4

Paunzen

Hümmerich

Bernhard

2021

A&A

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Aims. The present work presents our efforts at identifying new mercury-manganese (HgMn/CP3) stars using spectra obtained with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Methods. Suitable candidates were searched for among pre-selected early-type spectra from LAMOST DR4 using a modified version of the MKCLASS code that probes several Hg ii and Mn ii features. The spectra of the resulting 332 candidates were visually inspected. Using parallax data and photometry from Gaia DR2, we investigated magnitudes, distances from the Sun, and the evolutionary status of our sample stars. We also searched for variable stars using diverse photometric survey sources. Results. We present 99 bona fide CP3 stars, 19 good CP3 star candidates, and seven candidates. Our sample consists of mostly new discoveries and contains, on average, the faintest CP3 stars known (peak distribution 9.5 ≤ G ≤ 13.5 mag). All stars are contained within the narrow spectral temperature-type range from B6 to B9.5, in excellent agreement with the expectations and the derived mass estimates (2.4 ≤ M ⊙ ≤ 4 for most objects). Our sample stars are between 100 Myr and 500 Myr old and cover the whole age range from zero-age to terminal-age main sequence. They are almost homogeneously distributed at fractional ages on the main sequence ≤ 80 %, with an apparent accumulation of objects between fractional ages of 50 % to 80 %. We find a significant impact of binarity on the mass and age estimates. Eight photometric variables were discovered, most of which show monoperiodic variability in agreement with rotational modulation. Conclusions. Together with the recently published catalogue of APOGEE CP3 stars, our work significantly increases the sample size of known Galactic CP3 stars, paving the way for future in-depth statistical studies.

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Section: Colour-magnitude Diagrammentioning

confidence: 59%

New mercury-manganese stars and candidates from LAMOST DR4

Paunzen

Hümmerich

Bernhard

2021

A&A

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“…The first stage of the LAMOST spectroscopic survey [22][23][24][25] was carried out in a low-resolution (R ∼ 2000) mode with a wide spectral wavelength coverage of 3800-9000 Å. Based on abundances from APOGEE DR14 by Ting et al [26], Xiang et al [27] developed a data-driven neural network and derived stellar parameters and [α/Fe] abundances for 8162566 stars from LAMOST DR5. This is an internally consistent dataset (hereafter DDPayne-LAMOST DR5) and thus becomes a good sample for a statistic study.…”

Section: Selection Of Star Samplesmentioning

confidence: 99%

Low-α metal-rich stars with sausage kinematics in the LAMOST survey: Are they from the Gaia-Sausage-Enceladus galaxy?

Zhao

Chen

2021

Sci. China Phys. Mech. Astron.

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We search for metal-rich Sausage-kinematic (MRSK) stars with [Fe/H] > −0.8 and −100 < V ϕ < 50 km/s in LAMOST DR5 in order to investigate the influence of the Gaia-Sausage-Enceladus (GSE) merger event on the Galactic disk. For the first time, we find a group of low-α MRSK stars, and classify it as a metal-rich tail of the GSE galaxy based on the chemical and kinematical properties. This group has slightly larger R apo , Z max and E tot distributions than a previously-reported high-α group. Its low-α ratio does not allow for an origin resulting from the splash process of the GSE merger event, as is proposed to explain the high-α group. A hydrodynamical simulation by Amarante et al. provides a promising solution, in which the GSE galaxy is a clumpy Milky-Way analogue that develops a bimodal disk chemistry. This scenario explains the existence of MRSK stars with both high-α and low-α ratios found in this work. It is further supported by another new feature that a clump of MRSK stars is located at Z max =3-5 kpc, which corresponds to the widely adopted disk-halo transition at |Z| ∼ 4 kpc. We suggest that a pile-up of MRSK stars at Z max contributes significantly to this disk-halo transition, an interesting imprint left by the GSE merger event. These results also provide an important implication on the connection between the GSE and the Virgo Radial Merger.

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“…assumed single-star spectra. The binarity would be revealed in case of a significant mismatch between the two parallaxes, and this approach is discussed and attempted in Xiang et al (2019). Similarly, Cotar et al (2019) identified objects that are more luminous than predicted by their spectral type and Gaia distance, and specifically focused on double and triple Sun-like stars.…”

Section: Identification Of Binary Starsmentioning

confidence: 99%

“…spectra of solar-type stars. A proper investigation of this effect is therefore essential in order to make the findings of current and future projects dedicated to Galactic archaeology more reliable (see also Xiang et al 2019). To some extent, as indicated in Fig.…”

Section: Undetected Binarity and The Effect On Stellar Parametersmentioning

confidence: 99%

“…1) and its data-driven counterparts (see e.g. Xiang et al 2019). Additionally, there are other complex physical aspects of flux modelling that might be crucial for our work, such as proper treatment of the limb darkening and rotational velocity that it depends on, the effects of which can for example change the fitted T eff .…”

Section: Improvements Of the Model And The Fitting Proceduresmentioning

confidence: 99%

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The GALAH survey: multiple stars and our Galaxy

Traven

Feltzing

Merle

et al. 2020

A&A

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Context. Binary stellar systems form a large fraction of the Galaxy’s stars. They are useful as laboratories for studying the physical processes taking place within stars, and must be correctly taken into account when observations of stars are used to study the structure and evolution of the Galaxy. The advent of large-scale spectroscopic and photometric surveys allows us to obtain large samples of binaries that permit characterising their populations. Aims. We aim to obtain a large sample of double-lined spectroscopic binaries (SB2s) by analysis of spectra from the GALAH survey in combination with photometric and astrometric data. A combined analysis will provide stellar parameters of thousands of binary stars that can be combined to form statistical observables of a given population. We aim to produce a catalogue of well-characterised systems, which can in turn be compared to models of populations of binary stars, or to follow-up individual systems of interest. Methods. We obtained a list of candidate SB2 systems from a t-distributed stochastic neighbour embedding (t-SNE) classification and a cross-correlation analysis of GALAH spectra. To compute parameters of the primary and secondary star, we used a Bayesian approach that includes a parallax prior from Gaia DR2, spectra from GALAH, and apparent magnitudes from APASS, Gaia DR2, 2MASS, and WISE. We used a Markov chain Monte Carlo approach to sample the posterior distributions of the following model parameters for the two stars: Teff[1,2], logg[1,2], [Fe/H], Vr[1,2], vmic[1,2], vbroad[1,2], R[1,2], and E(B−V). Results. We present results for 12 760 binary stars detected as SB2s. We construct the statistical observables T1∕T2, ΔVr, and R1∕R2, which demonstrate that our sample mostly consists of dwarfs, with a significant fraction of evolved stars and several dozen members of the giant branch. The majority of these binary stars is concentrated at the lower boundary of the ΔVr distribution, and the R1∕R2 ratio is mostly close to unity. The derived metallicity of our binary stars is statistically lower than that of single dwarf stars from the same magnitude-limited sample. Conclusions. Our sample of binary stars represents a large population of well-characterised double-lined spectroscopic binaries that are appropriate for statistical studies of the binary populations. The derived stellar properties and their distributions show trends that are expected for a population of close binary stars (a < 10 AU) detected through double lines in their spectra. Our detection technique allows us to probe binary systems with mass ratios 0.5 ≤q ≤ 1.

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Abundance Estimates for 16 Elements in 6 Million Stars from LAMOST DR5 Low-Resolution Spectra

Cited by 198 publications

References 96 publications

New mercury-manganese stars and candidates from LAMOST DR4

New mercury-manganese stars and candidates from LAMOST DR4

Low-α metal-rich stars with sausage kinematics in the LAMOST survey: Are they from the Gaia-Sausage-Enceladus galaxy?

The GALAH survey: multiple stars and our Galaxy

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