The new record holder for the most iron-poor star: HE 1327–2326, a dwarf or subgiant with [Fe/H[=−5.4

Frebel, Anna; Aoki, Wako; Christlieb, N.; Ando, Hiroyasu; Asplund, Martin; Barklem, P. S.; Eriksson, K.; Fechner, C.; Fujimoto, Masayuki Y.; Honda, Satoshi; Kajino, Toshitaka; Minezaki, Takeo; Nomoto, Ken’ichi; Norris, John E.; Ryan, Sean G.; Takada-Hidai, Masahide; Tsangarides, Stelios; Yoshii, Yuzuru

doi:10.1017/s1743921305005569

Cited by 5 publications

(2 citation statements)

References 9 publications

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Section: Methodsmentioning

confidence: 95%

Network calculations for cosmochronometric studies

Petermann¹

2011

IJFPS

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The determinations of the age of the oldest objects in the universe, giving a lower limit of the age of the universe itself, are of great interest in astrophysics and cosmology. With the detection of the long-lived isotopes of thorium and uranium in a single star, their application as cosmochronometers has become possible. With network calculations, the production of Th and U can be studied for different input of the underlying mass model and the astrophysical environment. A comparison with the abundance pattern of very metal-poor stars can serve as a reference to check the validity of the assumptions and to better understand their influences on the final outcomes of the calculations. Once the initial amount of thorium and uranium are known, age estimations of stellar objects can be accomplished. Network calculations were performed that allow flexibly changing and studying the astrophysical environment in a parametric way, as well as the underlying nuclear physics input in terms of the final abundance pattern. The network used here includes more than 7000 nuclei, reaching far outside in the neutron rich area. The most relevant fission processes were implicitly taken into account. For all three massmodels a good agreement between the final abundance pattern and the abundance distribution for six metal poor stars is demonstrated. Network calculations are thus an appropriate tool to study and analyze the production of the cosmochronometers Th and U, which can be used for age-determinations for stars. A more detailed study of their production paths is necessary to reduce uncertainties with respect to the underlying massmodel and astrophysical environment.

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Section: Methodsmentioning

confidence: 95%

Network calculations for cosmochronometric studies

Petermann¹

2011

IJFPS

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“…Well below that value was the star HE0107-5240 described in 2002 (Christlieb et al 2002) with a value of [Fe/H] as low as -5.3. Very recently an even lower metallicity, [Fe/H]=-5.4 was reported in 2005 (Frebel et al, 2005) for HE1327-2326. For cosmochronometric studies, the stars have to additionally show an increased amount of r -process elements.…”

Section: Methodsmentioning

confidence: 95%

Network calculations for cosmochronometric studies

2011

IJFPS

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Exploring the Universe with Metal-Poor Stars

Frebel

2012

The First Galaxies

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The early chemical evolution of the Galaxy and the Universe is vital to our understanding of a host of astrophysical phenomena. Since the most metal-poor Galactic stars (with metallicities down to [Fe/H] ∼ −5.5) are relics from the highredshift Universe, they probe the chemical and dynamical conditions of the Milky Way and the origin and evolution of the elements through nucleosynthesis. They also provide constraints on the nature of the first stars, their associated supernovae and initial mass function, and early star and galaxy formation. The Milky Way's dwarf satellites contain a large fraction (∼ 30%) of the known most metal-poor stars that have chemical abundances that closely resemble those of equivalent halo stars. This suggests that chemical evolution may be universal, at least at early times, and that it is driven by massive, energetic SNe. Some of these surviving, ultra-faint systems may show the signature of just one such Pop III star; they may even be surviving first galaxies. Early analogs of the surviving dwarfs may thus have played an important role in the assembly of the old Galactic halo whose formation can now be studied with stellar chemistry. Following the cosmic evolution of small halos in simulations of structure formation enables tracing the cosmological origin of the most metalpoor stars in the halo and dwarf galaxies. Together with future observations and additional modeling, many of these issues, including the reionization history of the Milky Way, may be constrained this way. The chapter concludes with an outlook about upcoming observational challenges and ways forward is to use metal-poor stars to constrain theoretical studies.

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The new record holder for the most iron-poor star: HE 1327–2326, a dwarf or subgiant with [Fe/H[=−5.4

Cited by 5 publications

References 9 publications

Network calculations for cosmochronometric studies

Network calculations for cosmochronometric studies

Network calculations for cosmochronometric studies

Exploring the Universe with Metal-Poor Stars

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