Metal‐poor stars observed with the automated planet finder telescope. <scp>III</scp>. <scp>CEMP</scp>‐no stars are the descendant of population <scp>III</scp> stars

Almusleh, Nour Aldein; Taani, Ali; Özdemir, S.; Rah, Maria; Al-Wardat, Mashhoor A.; Zhao, Gang; Mardini, Mohammad K.

doi:10.1002/asna.202113867

“…CEMP-no stars are the dominant fraction of stars with [Fe/ H] < -3.0 (e.g., Aoki et al 2007;Yoon et al 2016). Because of their low-metallicity nature and low abundances of neutroncapture elements, they are regarded as the likely direct descendants of Population III stars (Christlieb et al 2002;Frebel et al 2005;Caffau et al 2011;Keller et al 2014;Placco et al 2016;Yoon et al 2016;Hartwig et al 2018;Starkenburg et al 2018;Almusleh et al 2021;. The C and O enrichment of CEMP-no stars is expected to have a profound impact on the formation of low-mass stars, since these species play a major role as efficient gas coolants, so that low-mass stars can form in even extremely low-metallicity environments (Bromm & Loeb 2003;Norris et al 2013;Frebel & Norris 2015).…”

Section: Introductionmentioning

confidence: 99%

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

Jeong

¹

,

Placco

²

,

Kim

³

et al. 2023

ApJ

3

1

0

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We present stellar parameters and abundances of 13 elements for 18 very metal-poor (VMP; [Fe/H] < –2.0) stars, selected as extremely metal-poor (EMP; [Fe/H] < –3.0) candidates from the Sloan Digital Sky Survey and Large sky Area Multi-Object Fiber Spectroscopic Telescope survey. High-resolution spectroscopic observations were performed using GEMINI-N/GRACES. We find 10 EMP stars among our candidates, and we newly identify three carbon-enhanced metal-poor stars with [Ba/Fe] < 0. Although chemical abundances of our VMP/EMP stars generally follow the overall trend of other Galactic halo stars, there are a few exceptions. One Na-rich star ([Na/Fe] = +1.14) with low [Mg/Fe] suggests a possible chemical connection with second-generation stars in a globular cluster. The progenitor of an extremely Na-poor star ([Na/Fe] = –1.02) with high K- and Ni-abundance ratios may have undergone a distinct nucleosynthesis episode, associated with core-collapse supernovae (SNe) having a high explosion energy. We have also found a Mg-rich star ([Mg/Fe] = +0.73) with slightly enhanced Na and extremely low [Ba/Fe], indicating that its origin is not associated with neutron-capture events. On the other hand, the origin of the lowest Mg abundance ([Mg/Fe] = –0.61) star could be explained by accretion from a dwarf galaxy, or formation in a gas cloud largely polluted by SNe Ia. We have also explored the progenitor masses of our EMP stars by comparing their chemical-abundance patterns with those predicted by Population III SNe models, and find a mass range of 10–26 M ⊙, suggesting that such stars were primarily responsible for the chemical enrichment of the early Milky Way.

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“…Umeda & Nomoto 2003Iwamoto et al 2005;Tominaga et al 2007;Ishigaki et al 2014;Bonifacio et al 2015). Recent models comparing the chemical abundances of five CEMP-no stars and the predicted SN yields confirm that SNe with a stellar mass of 11-22 M ⊙ and low explosion energies, 0.3-1.8×10 51 erg, are possible progenitors of CEMP-no stars (Almusleh et al 2021). However, massive and fast-rotating low-metallicity 'spinstars' have also been proposed as possible sources of enrichment for the birth environment of CEMP-no stars (Meynet et al 2006;Maeder et al 2015).…”

Section: Spite Et Al (2013bmentioning

confidence: 81%

The pristine nature of SMSS 1605−1443 revealed by ESPRESSO

Aguado¹,

Caffau²,

Molaro³

et al. 2023

A&A

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Context. SMSS J160540.18−144323.1 is the carbon-enhanced metal-poor (CEMP) star with the lowest iron abundance ever measured, [Fe/H] = −6.2, which was first reported with the SkyMapper telescope. The carbon abundance is A(C) ≈ 6.1 in the low-C band, as the majority of the stars in this metallicity range. Yet, constraining the isotopic ratio of key species, such as carbon, sheds light on the properties and origin of these elusive stars.Aims. We performed high-resolution observations of SMSS 1605−1443 with the ESPRESSO spectrograph to look for variations in the radial velocity (v rad ) with time. These data have been combined with older MIKE and UVES archival observations to enlarge the temporal baseline. The 12 C/ 13 C isotopic ratio is also studied to explore the possibility of mass transfer from a binary companion. Methods. A cross-correlation function against a natural template was applied to detect v rad variability and a spectral synthesis technique was used to derive 12 C/ 13 C in the stellar atmosphere. Results. We confirm previous indications of binarity in SMSS 1605−1443 and measured a lower limit 12 C/ 13 C> 60 at more than a 3 σ confidence level, proving that this system is chemically unmixed and that no mass transfer from the unseen companion has happened so far. Thus, we confirm the CEMP-no nature of SMSS 1605−1443 and show that the pristine chemical composition of the cloud from which it formed is currently imprinted in its stellar atmosphere free of contamination.

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“…Umeda & Nomoto 2003Iwamoto et al 2005;Tominaga et al 2007;Ishigaki et al 2014;Bonifacio et al 2015). Recent models comparing the chemical abundances of five CEMP-no stars and the predicted SN yields confirm that SNe with a stellar mass of 11-22 M ⊙ and low explosion energies, 0.3-1.8×10 51 erg, are possible progenitors of CEMP-no stars (Almusleh et al 2021). However, massive and fast-rotating low-metallicity 'spinstars' have also been proposed as possible sources of enrichment for the birth environment of CEMPno stars (Meynet et al 2006;Maeder et al 2015).…”

Section: Spitementioning

confidence: 81%

The pristine nature of SMSS 1605$-$1443 revealed by ESPRESSO

Aguado,

Caffau,

Molaro

et al. 2023

Preprint

1

0

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Context. SMSS J160540.18−144323.1 is the carbon-enhanced metal-poor (CEMP) star with the lowest iron abundance ever measured, [Fe/H] = −6.2, which was first reported with the SkyMapper telescope. The carbon abundance is A(C) ≈ 6.1 in the low-C band, as the majority of the stars in this metallicity range. Yet, constraining the isotopic ratio of key species, such as carbon, sheds light on the properties and origin of these elusive stars.Aims. We performed high-resolution observations of SMSS 1605−1443 with the ESPRESSO spectrograph to look for variations in the radial velocity (v rad ) with time. These data have been combined with older MIKE and UVES archival observations to enlarge the temporal baseline. The 12 C/ 13 C isotopic ratio is also studied to explore the possibility of mass transfer from a binary companion. Methods. A cross-correlation function against a natural template was applied to detect v rad variability and a spectral synthesis technique was used to derive 12 C/ 13 C in the stellar atmosphere. Results. We confirm previous indications of binarity in SMSS 1605−1443 and measured a lower limit 12 C/ 13 C> 60 at more than a 3 σ confidence level, proving that this system is chemically unmixed and that no mass transfer from the unseen companion has happened so far. Thus, we confirm the CEMP-no nature of SMSS 1605−1443 and show that the pristine chemical composition of the cloud from which it formed is currently imprinted in its stellar atmosphere free of contamination.

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Metal‐poor stars observed with the automated planet finder telescope. III. CEMP‐no stars are the descendant of population III stars

Cited by 12 publications

References 57 publications

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

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

The pristine nature of SMSS 1605−1443 revealed by ESPRESSO

The pristine nature of SMSS 1605$-$1443 revealed by ESPRESSO

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