Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis

Jeong, Miji; Placco, Vinicius M.; Kim, Young Kwang; Koo, Jae‐Rim; Lee, Ho-Gyu; Yang, Soung-Chul

doi:10.3847/1538-4357/acc58a

Cited by 3 publications

(1 citation statement)

References 190 publications

(266 reference statements)

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“…Because most manganese and essentially no neutron-capture elements are synthesized in thermonuclear explosions, the relatively high [Mn/Fe] abundances combined with the relatively low [Sr/Fe] and [Ba/Fe] abundances in these three stars support the idea that they formed in environments dominated by thermonuclear nucleosynthesis. Our results are consistent with previous conclusions based on similar stars (e.g., Ivans et al 2003;Aoki et al 2014;Jeong et al 2023). As we will show, though, we are able to constrain specific thermonuclear explosion mechanisms.…”

Section: Discussionsupporting

confidence: 94%

Iron-rich Metal-poor Stars and the Astrophysics of Thermonuclear Events Observationally Classified as Type Ia Supernovae. I. Establishing the Connection

Reggiani,

Schlaufman,

Casey

2023

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The progenitor systems and explosion mechanisms responsible for the thermonuclear events observationally classified as Type Ia supernovae are uncertain and difficult to uniquely constrain using traditional observations of Type Ia supernova host galaxies, progenitors, light curves, and remnants. For the subset of thermonuclear events that are prolific producers of iron, we use published theoretical nucleosynthetic yields to identify a set of elemental abundance ratios infrequently observed in metal-poor stars but shared across a range of progenitor systems and explosion mechanisms: [Na, Mg, Co/Fe] < 0. We label stars with this abundance signature “iron-rich metal-poor,” or IRMP stars. We suggest that IRMP stars formed in environments dominated by thermonuclear nucleosynthesis and consequently that their elemental abundances can be used to constrain both the progenitor systems and explosion mechanisms responsible for thermonuclear explosions. We identify three IRMP stars in the literature and homogeneously infer their elemental abundances. We find that the elemental abundances of BD +80 245, HE 0533–5340, and SMSS J034249.53–284216.0 are best explained by the (double) detonations of sub-Chandrasekhar-mass CO white dwarfs. If our interpretation of IRMP stars is accurate, then they should be very rare in globular clusters and more common in the Magellanic Clouds and dwarf spheroidal galaxies than in the Milky Way’s halo. We propose that future studies of IRMP stars will quantify the relative occurrences of different thermonuclear event progenitor systems and explosion mechanisms.

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Section: Discussionsupporting

confidence: 94%

Iron-rich Metal-poor Stars and the Astrophysics of Thermonuclear Events Observationally Classified as Type Ia Supernovae. I. Establishing the Connection

Reggiani,

Schlaufman,

Casey

2023

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GHOST commissioning science results – II: a very metal-poor star witnessing the early galactic assembly

Sestito,

Hayes,

Venn

et al. 2024

Monthly Notices of the Royal Astronomical Society

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This study focuses on Pristine$\_180956.78$−294759.8 (hereafter P180956, [Fe/H] = −1.95 ± 0.02), a star selected from the Pristine Inner Galaxy Survey (PIGS), and followed-up with the recently commissioned Gemini High-resolution Optical SpecTrograph (GHOST) at the Gemini South telescope. The GHOST spectrograph’s high efficiency in the blue spectral region (3700 − 4800 Å) enables the detection of elemental tracers of early supernovae (e.g., Al, Mn, Sr, Eu). The star exhibits chemical signatures resembling those found in ultra-faint dwarf systems, characterised by very low abundances of neutron-capture elements (Sr, Ba, Eu), which are uncommon among stars in the Milky Way halo. Our analysis suggests that P180956 bears the chemical imprints of a small number (2 or 4) of low-mass hypernovae (∼10 − 15 M⊙), which are needed to mostly reproduce the abundance pattern of the light-elements (e.g., [Si, Ti/Mg, Ca] ∼0.6), and one fast-rotating intermediate-mass supernova (∼300 km/s, ∼80 − 120 M⊙), which is the main channel contributing to the high [Sr/Ba] (∼+1.2). The small pericentric (∼0.7 kpc) and apocentric (∼13 kpc) distances and its orbit confined to the plane (≲ 2 kpc), indicate that this star was likely accreted during the early Galactic assembly phase. Its chemo-dynamical properties suggest that P180956 formed in a system similar to an ultra-faint dwarf galaxy accreted either alone, as one of the low-mass building blocks of the proto-Galaxy, or as a satellite of Gaia-Sausage-Enceladus. The combination of Gemini’s large aperture with GHOST’s high efficiency and broad spectral coverage makes this new spectrograph one of the leading instruments for near-field cosmology investigations.

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GTC Follow-up Observations of Very Metal-poor Star Candidates from DESI

Allende Prieto,

Aguado,

González Hernández

et al. 2023

ApJ

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The observations from the Dark Energy Spectroscopic Instrument (DESI) will significantly increase the numbers of known extremely metal-poor stars by a factor of ∼10, improving the sample statistics to study the early chemical evolution of the Milky Way and the nature of the first stars. In this paper we report follow-up observations with high signal-to-noise ratio of nine metal-poor stars identified during the DESI commissioning with the Optical System for Imaging and Low-Resolution Integrated Spectroscopy (OSIRIS) instrument on the 10.4 m Gran Telescopio Canarias. The analysis of the data using a well-vetted methodology confirms the quality of the DESI spectra and the performance of the pipelines developed for the data reduction and analysis of DESI data.

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Search for Extremely Metal-poor Stars with Gemini-N/Graces. I. Chemical-abundance Analysis

Cited by 3 publications

References 190 publications

Iron-rich Metal-poor Stars and the Astrophysics of Thermonuclear Events Observationally Classified as Type Ia Supernovae. I. Establishing the Connection

Iron-rich Metal-poor Stars and the Astrophysics of Thermonuclear Events Observationally Classified as Type Ia Supernovae. I. Establishing the Connection

GHOST commissioning science results – II: a very metal-poor star witnessing the early galactic assembly

GTC Follow-up Observations of Very Metal-poor Star Candidates from DESI

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