Ian U. Roederer
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View article: Abundances of Rarely Detected s-process Elements Derived from the Ultraviolet Spectrum of the s-process-enhanced Metal-poor Star HD 196944
Abundances of Rarely Detected s-process Elements Derived from the Ultraviolet Spectrum of the s-process-enhanced Metal-poor Star HD 196944 Open
We present an analysis of the heavy-element abundances of HD 196944, a carbon-enhanced metal-poor (CEMP) star enriched with elements produced by the slow neutron-capture process (s-process). We obtained a new high-resolution ultraviolet (U…
View article: The <i>R</i>-process Alliance: Enrichment of <i>r</i>-process Elements in a Simulated Milky Way–like Galaxy
The <i>R</i>-process Alliance: Enrichment of <i>r</i>-process Elements in a Simulated Milky Way–like Galaxy Open
We study the formation of stars with varying amounts of heavy elements synthesized by the rapid neutron-capture process ( r -process) based on our detailed cosmological zoom-in simulation of a Milky Way–like galaxy with an N -body/smoothed…
View article: The Heavy Element Enrichment History of the Universe from Neutron Star Mergers with Habitable Worlds Observatory
The Heavy Element Enrichment History of the Universe from Neutron Star Mergers with Habitable Worlds Observatory Open
Understanding where elements were formed has been a key goal in astrophysics for nearly a century, with answers involving cosmology, stellar burning, and cosmic explosions. Since 1957, the origin of the heaviest elements (formed via the ra…
View article: Habitable Worlds Observatory: The Nature of the Astrophysical r-process
Habitable Worlds Observatory: The Nature of the Astrophysical r-process Open
We present the science case for characterizing the origin of the heaviest elements on the periodic table, with a focus on those produced by the rapid neutron-capture process (r-process), using the Habitable Worlds Observatory (HWO). High-r…
View article: Probing Abundance Variations Among Multiple Stellar Populations in the Metal-poor Globular Cluster NGC 2298 Using Gemini-South/GHOST*
Probing Abundance Variations Among Multiple Stellar Populations in the Metal-poor Globular Cluster NGC 2298 Using Gemini-South/GHOST* Open
Studying the abundances in metal-poor globular clusters is crucial for understanding the formation of the Galaxy and the nucleosynthesis processes in the early Universe. We observed 13 red-giant stars from the metal-poor globular cluster N…
View article: Probing Abundance Variations among Multiple Stellar Populations in the Metal-Poor Globular Cluster NGC 2298 using Gemini-South/GHOST
Probing Abundance Variations among Multiple Stellar Populations in the Metal-Poor Globular Cluster NGC 2298 using Gemini-South/GHOST Open
Studying the abundances in metal-poor globular clusters is crucial for understanding the formation of the Galaxy and the nucleosynthesis processes in the early Universe. We observed 13 red giant stars from the metal-poor globular cluster N…
View article: Atomic Transition Probabilities for UV and Optical Lines of Gd <scp>ii</scp>*
Atomic Transition Probabilities for UV and Optical Lines of Gd <span>ii</span>* Open
We report new branching fraction (BF) measurements for 156 ultraviolet and optical transitions of Gd ii . These transitions range in wavelength (wavenumber) from 2574 to 6766 Å (38,838–14,777 cm −1 ) and originate in one odd-parity and 11 …
View article: The R-Process Alliance: Hunting for gold in the near-UV spectrum of 2MASS J05383296–5904280
The R-Process Alliance: Hunting for gold in the near-UV spectrum of 2MASS J05383296–5904280 Open
Context . Over the past few years, the R -Process Alliance (RPA) has successfully carried out a search for stars that are highly enhanced in elements produced via the rapid neutron-capture ( r -) process. In particular, the RPA has identif…
View article: Atomic Transition Probabilities for UV and Optical Lines of Gd II
Atomic Transition Probabilities for UV and Optical Lines of Gd II Open
We report new branching fraction measurements for 156 ultraviolet and optical transitions of Gd II. These transitions range in wavelength (wavenumber) from 2574 to 6766 Angstroms (38838 - 14777 cm-1) and originate in one odd-parity and 11 …
View article: New Stellar Parameters, Metallicities, and Elemental Abundance Ratios for 311 Metal-poor Stars
New Stellar Parameters, Metallicities, and Elemental Abundance Ratios for 311 Metal-poor Stars Open
We present equivalent widths, improved model atmosphere parameters, and revised abundances for 14 species of 11 elements derived from high-resolution optical spectroscopy of 311 metal-poor stars. All of these stars had their parameters pre…
View article: Discovery and Spectroscopic Confirmation of Aquarius III: A Low-mass Milky Way Satellite Galaxy
Discovery and Spectroscopic Confirmation of Aquarius III: A Low-mass Milky Way Satellite Galaxy Open
We present the discovery of Aquarius III, an ultra-faint Milky Way satellite galaxy identified in the second data release of the DECam Local Volume Exploration survey. Based on deeper follow-up imaging with DECam, we find that Aquarius III…
View article: BD+44°493: Chemo-dynamical Analysis and Constraints on Companion Planetary Masses from WIYN/NEID Spectroscopy*
BD+44°493: Chemo-dynamical Analysis and Constraints on Companion Planetary Masses from WIYN/NEID Spectroscopy* Open
In this work, we present high-resolution ( R ∼ 100,000), high signal-to-noise ratio (S/N ∼ 800) spectroscopic observations for the well-known, bright, extremely metal-poor, carbon-enhanced star BD+44°493 . We determined chemical abundances…
View article: The $R$-Process Alliance: Enrichment of $r$-process Elements in a Simulated Milky Way-like Galaxy
The $R$-Process Alliance: Enrichment of $r$-process Elements in a Simulated Milky Way-like Galaxy Open
We study the formation of stars with varying amounts of heavy elements synthesized by the rapid neutron-capture process ($r$-process) based on our detailed cosmological zoom-in simulation of a Milky Way-like galaxy with an $N$-body/smoothe…
View article: BD+44 493: Chemo-Dynamical Analysis and Constraints on Companion Planetary Masses from WIYN/NEID Spectroscopy
BD+44 493: Chemo-Dynamical Analysis and Constraints on Companion Planetary Masses from WIYN/NEID Spectroscopy Open
In this work, we present high-resolution (R~100,000), high signal-to-noise (S/N~800) spectroscopic observations for the well-known, bright, extremely metal-poor, carbon-enhanced star BD+44 493. We determined chemical abundances and upper l…
View article: Discovery and Spectroscopic Confirmation of Aquarius III: A Low-Mass Milky Way Satellite Galaxy
Discovery and Spectroscopic Confirmation of Aquarius III: A Low-Mass Milky Way Satellite Galaxy Open
We present the discovery of Aquarius III, an ultra-faint Milky Way satellite galaxy identified in the second data release of the DECam Local Volume Exploration (DELVE) survey. Based on deeper follow-up imaging with DECam, we find that Aqua…
View article: The R-process Alliance: Fifth Data Release from the Search for R-process-enhanced Metal-poor Stars in the Galactic Halo with the GTC*
The R-process Alliance: Fifth Data Release from the Search for R-process-enhanced Metal-poor Stars in the Galactic Halo with the GTC* Open
Understanding the abundance pattern of metal-poor stars and the production of heavy elements through various nucleosynthesis processes offers crucial insights into the chemical evolution of the Milky Way, revealing primary sites and major …
View article: Discovery of a Metal-poor Red Giant Star with the Highest Ultralithium Enhancement
Discovery of a Metal-poor Red Giant Star with the Highest Ultralithium Enhancement Open
We present the discovery of 2MASS J05241392−0336543 (hereafter J0524−0336), a very metal-poor ([Fe/H] = −2.43 ± 0.16), highly r -process-enhanced ([Eu/Fe] = +1.34 ± 0.10) Milky Way halo field red giant star, with an ultrahigh Li abundance …
View article: Atomic Transition Probabilities for Ultraviolet and Optical Lines of Tm <scp>ii</scp> *
Atomic Transition Probabilities for Ultraviolet and Optical Lines of Tm <span>ii</span> * Open
We report new branching fraction measurements for 224 ultraviolet and optical transitions of Tm ii . These transitions range in wavelength (wavenumber) from 2350 to 6417 Å (42,532–15,579 cm −1 ) and originate in 13 odd-parity and 24 even-p…
View article: The R-Process Alliance: 2MASS J22132050–5137385, the Star with the Highest-known r-process Enhancement at [Eu/Fe] = +2.45*
The R-Process Alliance: 2MASS J22132050–5137385, the Star with the Highest-known r-process Enhancement at [Eu/Fe] = +2.45* Open
We present stellar parameters and chemical abundances of 47 elements detected in the bright ( V = 11.63) very metal-poor ([Fe/H] = −2.20 ± 0.12) star 2MASS J22132050−5137385. We observed this star using the Magellan Inamori Kyocera Echelle…
View article: The R-Process Alliance: 2MASS J22132050-5137385, the Star with the Highest-known r-process Enhancement at [Eu/Fe] = +2.45
The R-Process Alliance: 2MASS J22132050-5137385, the Star with the Highest-known r-process Enhancement at [Eu/Fe] = +2.45 Open
We present stellar parameters and chemical abundances of 47 elements detected in the bright (V = 11.63) very metal-poor ([Fe/H] = -2.20 +- 0.12) star 2MASS J22132050-5137385. We observed this star using the Magellan Inamori Kyocera Echelle…
View article: Abundances of Neutron-capture Elements in 62 Stars in the Globular Cluster Messier 15
Abundances of Neutron-capture Elements in 62 Stars in the Globular Cluster Messier 15 Open
M15 is a globular cluster with a known spread in neutron-capture elements. This paper presents abundances of neutron-capture elements for 62 stars in M15. Spectra were obtained with the Michigan/Magellan Fiber System spectrograph, covering…
View article: The <i>R</i>-Process Alliance: Analysis of limited-<i>r</i> stars
The <i>R</i>-Process Alliance: Analysis of limited-<i>r</i> stars Open
Context. In recent years, the R -Process Alliance (RPA) has conducted a successful search for stars that are enhanced in elements produced by the rapid neutron-capture ( r -)process. In particular, the RPA has uncovered a number of stars t…
View article: The R-Process Alliance: Analysis of Limited-r Stars
The R-Process Alliance: Analysis of Limited-r Stars Open
Context. In recent years, the R-Process Alliance (RPA) has conducted a successful search for stars enhanced in elements produced by the rapid neutron-capture (r-)process. In particular, the RPA has uncovered a number of stars strongly enri…
View article: Measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Ce</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>140</mml:mn></mml:mrow></mml:mmultiscripts><mml:mo stretchy="false">(</mml:mo><mml:mi mathvariant="normal">n</mml:mi><mml:mo>,</mml:mo><mml:mi>γ</mml:mi><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math> Cross Section at n_TOF and Its Astrophysical Implications for the Chemical Evolution of the Universe
Measurement of the Cross Section at n_TOF and Its Astrophysical Implications for the Chemical Evolution of the Universe Open
Ce140(n,γ) is a key reaction for slow neutron-capture (s-process) nucleosynthesis due to being a bottleneck in the reaction flow. For this reason, it was measured with high accuracy (uncertainty ≈5%) at the n_TOF facility, with an unpreced…
View article: Abundances of Neutron-Capture Elements in 62 Stars in the Globular Cluster Messier 15
Abundances of Neutron-Capture Elements in 62 Stars in the Globular Cluster Messier 15 Open
M15 is a globular cluster with a known spread in neutron-capture elements. This paper presents abundances of neutron-capture elements for 62 stars in M15. Spectra were obtained with the Michigan/Magellan Fiber System (M2FS) spectrograph, c…
View article: The <i>R</i>-Process Alliance: detailed chemical composition of an <i>r</i>-process enhanced star with UV and optical spectroscopy
The <i>R</i>-Process Alliance: detailed chemical composition of an <i>r</i>-process enhanced star with UV and optical spectroscopy Open
We present a detailed chemical-abundance analysis of a highly r-process-enhanced (RPE) star, 2MASS J00512646-1053170, using high-resolution spectroscopic observations with Hubble Space Telescope/STIS in the UV and Magellan/MIKE in the opti…
View article: The $R$-Process Alliance: Detailed Composition of an $R$-Process Enhanced Star with UV and Optical Spectroscopy
The $R$-Process Alliance: Detailed Composition of an $R$-Process Enhanced Star with UV and Optical Spectroscopy Open
We present a detailed chemical-abundance analysis of a highly $r$-process enhanced (RPE) star, 2MASS J00512646-1053170, using high-resolution spectroscopic observations with $Hubble\ Space\ Telescope$/STIS in the UV and Magellan/MIKE in th…
View article: The <em>R</em>-process Alliance: A Nearly Complete <em>R</em>-process Abundance Template Derived from Ultraviolet Spectroscopy of the <em>R</em>-process-enhanced Metal-poor Star HD 222925<sup>*</sup>
The <em>R</em>-process Alliance: A Nearly Complete <em>R</em>-process Abundance Template Derived from Ultraviolet Spectroscopy of the <em>R</em>-process-enhanced Metal-poor Star HD 222925<sup>*</sup> Open
We present a nearly complete rapid neutron-capture process (r-process) chemical inventory of the metal-poor ([Fe/H] = -1.46 ± 0.10) r-process-enhanced ([Eu/Fe] = +1.32 ± 0.08) halo star HD 222925. This abundance set is the most complete fo…
View article: Element abundance patterns in stars indicate fission of nuclei heavier than uranium
Element abundance patterns in stars indicate fission of nuclei heavier than uranium Open
The heaviest chemical elements are naturally produced by the rapid neutron-capture process ( r -process) during neutron star mergers or supernovae. The r -process production of elements heavier than uranium (transuranic nuclei) is poorly u…
View article: SPLUS J142445.34–254247.1: An r-process–enhanced, Actinide-boost, Extremely Metal-poor Star Observed with GHOST
SPLUS J142445.34–254247.1: An r-process–enhanced, Actinide-boost, Extremely Metal-poor Star Observed with GHOST Open
We report on a chemo-dynamical analysis of SPLUS J142445.34−254247.1 (SPLUS J1424−2542), an extremely metal-poor halo star enhanced in elements formed by the rapid neutron-capture process ( r -process). This star was first selected as a me…