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We have performed a differential, line-by-line, chemical abundance analysis, ultimately relative to the Sun, of nine very metal-poor main sequence halo stars, near [Fe/H]=$-$2 dex. Our abundances range from…

Solar and Stellar Astrophysics · Physics 2017-04-05 Erin O'Malley , Andrew McWilliam , Brian Chaboyer , Ian Thompson

We have shown that data-driven models are effective for inferring physical attributes of stars (labels; Teff, logg, [M/H]) from spectra, even when the signal-to-noise ratio is low. Here we explore whether this is possible when the…

Solar and Stellar Astrophysics · Physics 2016-03-11 Andrew R. Casey , David W. Hogg , Melissa Ness , Hans-Walter Rix , Anna Q Y Ho , Gerry Gilmore

We report the first detailed chemical abundances for 5 globular clusters (GCs) in M31 from high-resolution (R ~ 25,000) spectroscopy of their integrated light. These GCs are the first in a larger set of clusters observed as part of an…

Astrophysics of Galaxies · Physics 2015-05-14 J. E. Colucci , R. A. Bernstein , S. Cameron , A. McWilliam , J. G. Cohen

We map the trends of elemental abundance ratios across the Galactic disk, spanning R = 3-15 kpc and midplane distance |Z|= 0-2 kpc, for 15 elements in a sample of 20,485 stars measured by the SDSS/APOGEE survey (O, Na, Mg, Al, Si, P, S, K,…

We present an analysis of a large sample of moderate resolution Keck LRIS spectra of subgiants and stars at the base of the RGB in M15, most within the range 16.5 < V < 19.5 (1.2 < M_V < 4.2), with the goal of deriving C abundances (from…

Astrophysics · Physics 2008-11-26 Judith G. Cohen , Michael M. Briley , Peter B. Stetson

Stellar parameters and abundances provide crucial insights into stellar and Galactic evolution studies. In this work, we developed a convolutional neural network (CNN) to estimate stellar parameters: effective temperature…

Astrophysics of Galaxies · Physics 2025-06-23 Haoyang Liu , Cuihua Du , Mingji Deng , Jian Zhang

Chemical abundances for 15 elements (C, N, O, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, and Ni) are presented for 83 stellar members of the 4 Gyr old solar-metallicity open cluster M67. The sample contains stars spanning a wide range of…

The first generations of stars left their chemical fingerprints on metal-poor stars in the Milky Way and its surrounding dwarf galaxies. While instantaneous and homogeneous enrichment implies that groups of co-natal stars should have the…

Astrophysics of Galaxies · Physics 2024-10-16 Jennifer Mead , Melissa Ness , Eric Andersson , Emily J. Griffith , Danny Horta

In preparation for future, large-scale, multi-object, high-resolution spectroscopic surveys of the Galaxy, we present a series of tests of the precision in radial velocity and chemical abundances that any such project can achieve at a 4m…

Detailed chemical analyses of M dwarfs are scarce but necessary to constrain the formation environment and internal structure of planets being found around them. We present elemental abundances of 13 M dwarfs (2900 < Teff < 3500 K) observed…

We present a detailed study of the composition of 20 M giants in the Galactic center with 15 of them confirmed to be in the Nuclear Star Cluster. As a control sample we have also observed 7 M giants in the Milky Way Disk with similar…

We present a novel approach to deriving stellar labels for stars observed in MUSE fields making use of data-driven machine learning methods. Taking advantage of the comparable spectral properties (resolution, wavelength coverage) of the…

Solar and Stellar Astrophysics · Physics 2022-05-27 Zixian Wang , Michael R. Hayden , Sanjib Sharma , Maosheng Xiang , Yuan-Sen Ting , Joss Bland-Hawthorn , Boquan Chen

The abundance of {\alpha}-elements provides an important fossil signature in Galactic archaeology to trace the chemical evolution of the different disc populations. High-precision chemical abundances are crucial to improving our…

We have derived Mn abundances for more than 200 stars in 19 globular clusters. In addition, Mn abundance determinations have been made for a comparable number of halo field and disk stars possessing an overlapping range of metallicities and…

Using multi-element abundances from the SDSS APOGEE survey, we investigate the origin of abundance variations in Milky Way (MW) disk stars on the "high-$\alpha$ plateau," with $-0.5\leq\rm{[Mg/H]}\leq-0.1$ and…

Astrophysics of Galaxies · Physics 2025-09-25 Tawny Sit , David H. Weinberg , Emily J. Griffith

The ``2-process Model'' is a promising technique for interpreting stellar chemical abundance data from large-scale surveys (e.g., SDSS-IV/V, GALAH), enabling more quantitative empirical studies of differences in chemical enrichment history…

Large-scale spectroscopic surveys have collectively observed millions of stars across the Milky Way, but each derives stellar labels using independent pipelines with distinct modelling assumptions, introducing systematic offsets that…

Astrophysics of Galaxies · Physics 2026-04-29 Jeff Shen , Joshua S. Speagle , Shirley Ho

In this paper we refine our method for the abundance analysis of high resolution spectroscopy of the integrated light of unresolved globular clusters (GCs). This method was previously demonstrated for the analysis of old ($>$10 Gyr) Milky…

Astrophysics of Galaxies · Physics 2015-05-27 J. E. Colucci , R. A. Bernstein , S. A. Cameron , A. McWilliam

We investigate the [X/Mg] abundances of 16 elements for 82,910 Galactic disk stars from GALAH+ DR3. We fit the median trends of low-Ia and high-Ia populations with a two-process model, which describes stellar abundances in terms of a prompt…

Astrophysics of Galaxies · Physics 2022-05-25 Emily J. Griffith , David H. Weinberg , Sven Buder , Jennifer A. Johnson , James W. Johnson , Fiorenzo Vincenzo

Chemical clocks offer a powerful tool for estimating stellar ages from spectroscopic surveys. We present a new detailed spectroscopic analysis of 68 Kepler red giant stars to provide a suite of high-precision abundances along with…

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