211 citations · 1.4k across the 46 of their papers we have counts for
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Bright Metal-Poor Star Survey - I. Tomo-e Gozen narrow-band photometric survey and medium-resolution spectroscopic follow-up
Hiroko Okada, Takumi Iwasaki, Nozomu Tominaga +21
We present the Tomo-e Gozen Bright Metal-Poor Star Survey (TeMPS), a wide-area narrow-band photometric survey for bright metal-poor stars in the northern sky. The survey uses the T…
Revealing α-Element's Past with Subaru/IRD: Oxygen Abundance of 35 Very Metal-Poor Stars from Near-IR OH lines
Bakuh Danang Setyo Budi, Wako Aoki, Nicholas Storm +10
Oxygen abundances in very and extremely metal-poor (V/EMP) stars provide critical constraints on early massive stars' nucleosynthesis. An Oxygen abundance analysis is presented for…
A Systematic NLTE Study of Very Metal-Poor Stars with Metallicity Down to dex. II. Lithium Abundance and New Insight to the Lithium Plateau
Hong-Liang Yan, Jinxiao Qin, Shuai Liu +12
Metal-poor stars are crucially important for understanding the early Galaxy, first stars, and the Universe. In this series of papers, we present a homogeneous non-local thermodynam…
A nearly pristine star from the Large Magellanic Cloud
Alexander P. Ji, Vedant Chandra, Selenna Mejias-Torres +28
The first stars formed out of pristine gas, causing them to be so massive that none are expected to have survived until today. If their direct descendants were sufficiently low-mas…
Th/Eu abundance ratio of red giants in the Kepler Field
Ainun Azhari, Tadafumi Matsuno, Wako Aoki +2
The r-process production in the early universe has been well constrained by the extensive studies of metal-poor stars. However, the r-process enrichment in the metal-rich regime is…
Elemental abundances of 44 very metal-poor stars determined from Subaru/IRD near-infrared spectra
Wako Aoki, Timothy C. Beers, Satoshi Honda +12
Abundances of five elements, Na, Mg, Al, Si, and Sr, are investigated for 44 very metal-poor stars (-4.0 < [Fe/H] < -1.5) in the Galactic halo system based on an Local Thermodinami…
Unevolved Li-rich stars at low metallicity: a possible formation pathway through novae
Tadafumi Matsuno, Alex Kemp, Ataru Tanikawa +7
A small fraction of low-mass stars have been found to have anomalously high Li abundances. Although it has been suggested that mixing during the red giant branch phase can lead to…
A distinct halo population revealed from 3D non-LTE magnesium abundances
T. Matsuno, A. M. Amarsi, M. Carlos +1
Magnesium is one of the important elements in stellar physics as an electron donor and in Galactic Archaeology as a discriminator of different stellar populations. However, previou…
Unique chemical composition of the very metal-poor star LAMOST J1645+4357
Wako Aoki, Haining Li, Nozomu Tominaga +3
We report on the chemical composition of the very metal-poor ([Fe/H]=-2.9) star LAMOST J1645+4357 that is identified to be a red giant having peculiar abundance ratios by Li et al.…
Improving metallicity estimates for very metal-poor stars in the Gaia DR3 GSP-Spec catalog
Tadafumi Matsuno, Else Starkenburg, Eduardo Balbinot +1
The Gaia DR3 GSP-Spec parameters, including metallicity, for VMP stars suffer from parameter degeneracy due to a lack of information in their spectra. Furthermore, the recommended…
Gaia DR2 and EDR3 data and evolutionary status of post-AGB stars with high radial velocities
Wako Aoki, Tadafumi Matsuno, Mudumba Parthasarathy
Using the Gaia DR2 and EDR3 data and list of post-AGB candidates, we investigate the parallax, proper motion and binarity for twenty post-AGB stars and candidates having high radia…
Four-hundred Very Metal-Poor Stars Studied with LAMOST and Subaru. II. Elemental abundances
Haining Li, Wako Aoki, Tadafumi Matsuno +9
We present homogeneous abundance analysis of over 20 elements for 385 very metal-poor (VMP) stars based on the LAMOST survey and follow-up observations with the Subaru Telescope. I…
Four-hundred Very Metal-poor Stars studied with LAMOST and Subaru. I. Survey Design, Follow-up Program, and Binary Frequency
Wako Aoki, Haining Li, Tadafumi Matsuno +11
The chemical abundances of very metal-poor stars provide important constraints on the nucleosynthesis of the first generation of stars and early chemical evolution of the Galaxy. W…
Silicon and Strontium abundances of very metal-poor stars determined from near-infrared spectra
Wako Aoki, Timothy C. Beers, Satoshi Honda +19
Silicon and Strontium are key elements to explore the nucleosynthesis and chemical evolution of the Galaxy by measurements of very metal-poor stars. There are, however, only a few…
First Star Survivors as Metal-Rich Halo Stars that Experienced Supernova Explosions in Binary Systems
Takuma Suda, Takayuki R. Saitoh, Yuki Moritani +2
The search for the first stars formed from metal-free gas in the universe is one of the key issues in astronomy because it relates to many fields, such as the formation of stars an…
Most Lithium-rich Low-mass Evolved Stars Revealed as Red Clump stars by Asteroseismology and Spectroscopy
Hong-Liang Yan, Yu-Tao Zhou, Xianfei Zhang +19
Lithium has confused scientists for decades at almost each scale of the universe. Lithium-rich giants are peculiar stars with lithium abundances over model prediction. A large frac…
Gaia DR 2 data and the evolutionary status of eight high velocity hot post-AGB candidates
Mudumba Parthasarathy, Tadafumi Matsuno, Wako Aoki
From Gaia DR 2 data of eight high velocity hot post-AGB candidates LS 3593, LSE 148, LS 5107, HD 172324, HD 214539, LS IV -12 111, LS III +52 24, and LS 3099, we found that six of…
Star Formation Timescales of the Halo Populations from Asteroseismology and Chemical Abundances
Tadafumi Matsuno, Wako Aoki, Luca Casagrande +9
We combine asteroseismology, optical high-resolution spectroscopy, and kinematic analysis for 26 halo red giant branch stars in the \textit{Kepler} field in the range of $-2.5<[\ma…
Evidence for the accretion origin of halo stars with an extreme r-process enhancement
Qian-Fan Xing, Gang Zhao, Wako Aoki +4
Small stellar systems like dwarf galaxies are suggested to be the main building blocks of our Galaxy by numerical simulations in Lambda CDM models. The existence of star streams li…
LAMOST J2217+2104: a new member of carbon-enhanced extremely metal-poor stars with excesses of Mg and Si
Wako Aoki, Tadafumi Matsuno, Satoshi Honda +4
We report on the elemental abundances of the carbon-enhanced metal-poor (CEMP) star J2217+2104 discovered by our metal-poor star survey with LAMOST and Subaru. This object is a red…
Optical high-resolution spectroscopy of 14 young -rich stars
Tadafumi Matsuno, David Yong, Wako Aoki +1
We report chemical abundances of 14 young -rich stars including neutron-capture elements based on high-quality optical spectra from HIRES/Keck I and differential line-by-line an…
Enormous Li-enhancement preceding red giant phases in low-mass stars in the Milky Way halo
Haining Li, Wako Aoki, Tadafumi Matsuno +4
Li abundances in the bulk of low-mass metal-poor stars are well reproduced by stellar evolution models adopting a constant initial abundance. However, a small number of stars have…
Enrichment in r-process elements from multiple distinct events in the early Draco dwarf spheroidal galaxy
Takuji Tsujimoto, Tadafumi Matsuno, Wako Aoki +2
The stellar record of elemental abundances in satellite galaxies is important to identify the origin of r-process because such a small stellar system could have hosted a single r-p…
High-resolution spectroscopy of extremely metal-poor stars from SDSS/SEGUE. III. Unevolved Stars with
Tadafumi Matsuno, Wako Aoki, Timothy C. Beers +2
We present elemental abundances for eight unevolved extremely metal-poor stars with , among which seven have . The sample is sel…