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M dwarfs are prominent targets of planet search projects, and their chemical composition is crucial to understanding the formation process or interior of orbiting exoplanets. However, measurements of elemental abundances of M dwarfs have…

Solar and Stellar Astrophysics · Physics 2020-12-30 Hiroyuki Tako Ishikawa , Wako Aoki , Takayuki Kotani , Masayuki Kuzuhara , Masashi Omiya , Ansgar Reiners , Mathias Zechmeister

HARPS-N spectra with S/N > 250 and MARCS model atmospheres were used to derive abundances of C, O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, and Y in ten stars from the Kepler LEGACY sample (including the binary pair 16 Cyg A and B) selected…

Solar and Stellar Astrophysics · Physics 2017-12-13 P. E. Nissen , V. Silva Aguirre , J. Christensen-Dalsgaard , R. Collet , F. Grundahl , D. Slumstrup

Aims: We developed a new method of estimating the stellar parameters Teff, log g, [M/H], and elemental abundances. This method was implemented in a new code, SP_Ace (Stellar Parameters And Chemical abundances Estimator). This is a highly…

Instrumentation and Methods for Astrophysics · Physics 2016-02-17 C. Boeche , E. K. Grebel

By measuring the elemental abundances of a star, we can gain insight into the composition of its initial gas cloud -- the formation site of the star and its planets. Planet formation requires metals, the availability of which is determined…

Earth and Planetary Astrophysics · Physics 2021-09-02 Jared R. Kolecki , Ji Wang , Jennifer A. Johnson , Joel C. Zinn , Ilya Ilyin , Klaus G Strassmeier

The fundamental stellar atmospheric parameters T_eff and log g and 13 chemical abundances are derived for medium-resolution spectroscopy from LAMOST Medium-Resolution Survey (MRS) data sets with a deep-learning method. The neural networks…

Solar and Stellar Astrophysics · Physics 2020-03-11 Rui Wang , A-Li Luo , Jian-Jun Chen , Wen Hou , Shuo Zhang , Yong-Heng Zhao , Xiang-Ru Li , Yong-Hui Hou , LAMOST MRS Collaboration

[Abridged abstract] We have performed an abundance analysis for 176 F- and G- dwarfs of the Galactic thick disk component. Using accurate radial velocities combined with $Hipparcos$ astrometry, kinematics (U, V, and W) and Galactic orbital…

Astrophysics · Physics 2009-11-13 Bacham E. Reddy , David L. Lambert , Carlos Allende Prieto

The hydrogen-deficiency in extremely hot post-AGB stars of spectral class PG1159 is probably caused by a (very) late helium-shell flash or a AGB final thermal pulse that consumes the hydrogen envelope, exposing the usually-hidden intershell…

Solar and Stellar Astrophysics · Physics 2015-05-14 K. Werner

We present a series of systematic abundance measurements for 89 hot DA white dwarfs drawn from the FUSE observation archive. These stars span the temperature range ~ 20000-70000K, and form the largest sample to-date, exceeding our earlier…

Solar and Stellar Astrophysics · Physics 2013-02-27 M. A. Barstow , S. L. Casewell , J. B. Holberg , J. K. Barstow

Understanding the assembly of our Galaxy requires us to also characterize the systems that helped build it. In this work, we accomplish this by exploring the chemistry of accreted halo stars from the Gaia-Enceladus/Gaia-Sausage (GES)…

Solar and Stellar Astrophysics · Physics 2022-05-04 Andreia Carrillo , Keith Hawkins , Paula Jofré , Danielle de Brito Silva , Payel Das , Madeline Lucey

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 of stars uniformly distributed over the $-2.62 \le$ [Fe/H]…

To date, we have access to enormous inventories of stellar spectra that allow the extraction of atmospheric parameters and chemical abundances essential in stellar studies. However, characterizing such a large amount of data is complex and…

(abridged) Elemental abundances of FGK stars can be derived routinely from high-resolution optical spectra, but this remains considerably more difficult for cooler stars. Machine-learning methods offer a practical route to infer otherwise…

Deriving accurate carbon abundance estimates for a wide variety of stars is still complex due to the difficulties in properly measuring it from atomic and molecular lines. The aim of this paper is to analyse the carbon abundance…

We describe a method for the determination of stellar [C/Fe] abundance ratios using low-resolution (R = 2000) stellar spectra from the SDSS and SEGUE. By means of a star-by-star comparison with a set of SDSS/SEGUE spectra with available…

High-resolution optical spectra of 30 metal-poor stars selected from the \Pristine\ survey are presented, based on observations taken with the Gemini Observatory GRACES spectrograph. Stellar parameters \teff and \logg are determined using a…

Stars of a common origin are thought to have similar, if not nearly identical, chemistry. Chemical tagging seeks to exploit this fact to identify Milky Way subpopulations through their unique chemical fingerprints. In this work, we compare…

[Abridged] Investigations of neutron(n)-capture element nucleosynthesis and chemical evolution have largely been based on stellar spectroscopy. However, the recent detection of these elements in several planetary nebulae (PNe) indicates…

Data-driven models of stellar spectra are useful tools to study non-stellar information, such as the Diffuse Interstellar Bands (DIBs) caused by intervening interstellar material. Using $\sim 55000$ spectra of $\sim 17000$ red clump stars…

Astrophysics of Galaxies · Physics 2024-02-08 Kevin A. McKinnon , Melissa K. Ness , Constance M. Rockosi , Puragra Guhathakurta

We present observations and initial analysis from an HST/STIS program to obtain the first co-spatial, UV-optical spectra of ten Galactic planetary nebulae (PNe). Our primary objective was to measure the critical emission lines of carbon and…

Solar and Stellar Astrophysics · Physics 2015-06-23 Reginald J. Dufour , Karen B. Kwitter , Richard A. Shaw , Richard B. C. Henry , Bruce Balick , Romano L. M. Corradi

We develop and test a method for the estimation of metallicities ([Fe/H]) and carbon abundance ratios ([C/Fe]) for carbon-enhanced metal-poor (CEMP) stars, based on application of artificial neural networks, regressions, and synthesis…