Is HE 0107–5240 A Primordial Star? The Characteristics of Extremely Metal-Poor Carbon-Rich Stars

By T. Suda, M. Aikawa, Masahiro N. Machida, M. Fujimoto, Icko Iben, Jr.,. 2004

173 citations recorded by the source corpus.

We discuss the origin of HE 0107-5240, which, with a metallicity of [Fe/H] = -5.3, is the most iron-poor star yet observed. Its discovery has an important bearing on the question of the observability of first-generation stars in our universe. In common with other stars of very small metallicity (-4 ≲ [Fe/H] ≲ -2.5), HE 0107-5240 shows a peculiar abundance pattern, including large enhancements of C, N, and O, and a more modest enhancement of Na. The observed abundance pattern can be explained by nucleosynthesis and mass transfer in a first-generation binary star, which, after birth, accretes matter from a primordial cloud mixed with the ejectum of a supernova. We elaborate the binary scenario on the basis of our current understanding of the evolution and nucleosynthesis of extremely metal-poor, low-mass model stars and discuss the possibility of discriminating this scenario from others. In our picture, iron-peak elements arise in surface layers of the component stars by accretion of gas from the polluted primordial cloud, pollution occurring after the birth of the binary. To explain the observed C, N, O, and Na enhancements, as well as the 12C/ 13C ratio, we suppose that the currently observed star, once the secondary in a binary, accreted matter from a chemically evolved companion, which is now a white dwarf. To estimate the abundances in the matter transferred in the binary, we rely on the results of computations of model stars constructed with up-to-date input physics. Nucleosynthesis in a helium-flash-driven convective zone into which hydrogen has been injected is followed, allowing us to explain the origin in the primary of the observed O and Na enrichments and to discuss the abundances of s-process elements. From the observed abundances, we conclude that HE 0107-5240 has evolved from a wide binary (of initial separation ~20 AU) with a primary of initial mass in the range 1.2-3 M☉. On the assumption that the system now consists of a white dwarf and a red giant, the present binary separation and period are estimated at ≃34 AU and a period of ≃150 yr, respectively. We also conclude that the abundance distribution of heavy s-process elements may hold the key to a satisfactory understanding of the origin of HE 0107-5240. An enhancement of [Pb/Fe] ≃ 1-2 should be observed if HE 0107-5240 is a second-generation star, formed from gas already polluted with iron-group elements. If the enhancement of main-line s-process elements is not detected, HE 0107-5240 may be a first-generation secondary in a binary system with a primary of mass less than 2.5 M☉, born from gas of primordial composition, produced in the big bang, and subsequently subjected to surface pollution by accretion of gas from the parent cloud metal-enriched by mixing with the ejectum of a supernova.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/dacdeaafeee3ea72bde6161b52d6af2e4a1c02b4

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

Citations in the corpus

HE 1327–2326, an Unevolved Star with [Fe/H] < –5.0. I. A Comprehensive Abundance Analysis (2005, background): “Accretion from the ISMwas also investigated by Suda et al. (2004), who estimated the effect inside the starforming region to be significant.”
Neutron-Capture Elements in the Early Galaxy (2008, background): “…associated nucleosynthesis of light and n-capture elements during the TDU episodes for these very low-metallicity stars have been described by, e.g., Iwamoto et al. (2004); Suda et al. (2004); Suda, Fujimoto & Itoh (2007); Cristallo et al. (2006); Campbell (2007); and Campbell & Lattanzio (2008).”
Very low-metallicity massive stars: - Pre-SN evolution models and primary nitrogen production (2006, background): “About three quarters of the CEMPs show a standard s-process enrichment, which is best explained by accretion from an AGB companion in a binary system (Suda et al. 2004).”
Evolution and nucleosynthesis of extremely metal-poor and metal-free low- and intermediate-mass stars - I. Stellar yield tables and the CEMPs (2008, methodology): “Helium Flash Induced Mixing (HEFM, Schlattl et al. 2002) and Helium Flash-Driven Deep Mixing (He-FDDM, Suda et al. 2004).”
Nucleosynthesis in Stars and the Chemical Enrichment of Galaxies (2013, background): “Several scenarios, including a single supernova (e.g., Umeda & Nomoto 2002) and AGB stars in binary systems (Suda et al. 2004, Lugaro et al. 2008), have been proposed to explain the observed abundance ratios.”
THE MOST METAL-POOR STARS. IV. THE TWO POPULATIONS WITH [Fe/H] ≲ −3.0 (2012, methodology): “For the interest of the reader we also plot the position of the Suda et al. (2004) binary model for the C-rich star HE 0107–5240 (period 150 yrs, K1 = 7 km s−1).”
Near-Field Cosmology with Extremely Metal-Poor Stars (2015, background): “This topic has been considered by many authors in the recent literature, and we refer the reader to Fujimoto, Ikeda & Iben (2000), Suda et al. (2004), Beers & Christlieb (2005), Meynet, Ekström & Maeder (2006), Nomoto et al. (2006), Norris et al. (2007), Frebel et al. Lai et al. (2008), Cohen et…”
Galactic Chemical Evolution: Carbon through Zinc (2006, background): “…> 0.4 suggest other enrichment sources, which could be i) a single supernova (Umeda & Nomoto 2003; Iwamoto et al. 2005), namely, a faint supernova with E51 < 1), ii) a few supernovae (Limongi, Chieffi, & Bonifacio 2003), or iii) external enrichment from a binary companion (e.g., Suda et al. 2004).”
Binarity in carbon-enhanced metal-poor stars (2014, background): “On the other hand, it is yet insufficiently understood if carbon could be transferred from an AGB companion without s-process elements (e.g., Suda et al. 2004).”
Stellar Abundances for the Galactic Archeology (SAGA) Database — Compilation of the Characteristics of Known Extremely Metal-Poor Stars (2008, methodology): “We set the boundary between the EMP star (labeled “EMP”) and the other population II stars at [Fe/H] =−2.5, which is based on stellar evolution models for low- and intermediate-mass in which proton mixing driven by helium burning occurs for [Fe/H]<∼ −2.5 (Fujimoto et al. 2000; Suda et al. 2004).”
Evolution of Dust in Primordial Supernova Remnants: Can Dust Grains Formed in the Ejecta Survive and Be Injected into the Early Interstellar Medium? (2007, background): “…fallback in a corecollapse SN (Umeda & Nomoto 2005; Iwamoto et al. 2005), the nucleosynthesis and mass transfer in a first-generation binary star (Suda et al. 2004; Komiya et al. 2007), the pollution by the gas with heavy elements in the ISM (Shigeyama et al. 2003), and the combinations of these…”
The first stars: formation of binaries and small multiple systems (2009, background): “If one of the members of a Pop III binary was an intermediate-mass star (1 M⊙ <∼ M∗ <∼ 8 M⊙), then the companion might undergo carbon enhancement through binary mass-transfer (e.g. Suda et al. 2004).”
CONVECTIVE–REACTIVE PROTON–12C COMBUSTION IN SAKURAI'S OBJECT (V4334 SAGITTARII) AND IMPLICATIONS FOR THE EVOLUTION AND YIELDS FROM THE FIRST GENERATIONS OF STARS (2010, background): “…in numerous phases of stellar evolution, including the He-shell flash of AGB stars of extremely low metal content (e.g. Fujimoto et al. 2000; Suda et al. 2004; Iwamoto et al. 2004; Cristallo et al. 2009), metallicity low-mass stars (e.g. Hollowell et al. 1990; Schlattl et al. 2002; Campbell…”
The evolution of isotope ratios in the Milky Way Galaxy (2011, background): “A significant fraction of metal-poor stars show carbon en- richment (CEMP stars), with several scenarios proposed to explain the observed abundances including a single supernova (e.g., Umeda & Nomoto 2002) and AGB stars in binary systems (Suda et al. 2004; Lugaro et al. 2008; Izzard et al. 2009).”
HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS FROM SDSS/SEGUE. I. ATMOSPHERIC PARAMETERS AND CHEMICAL COMPOSITIONS (2012, background): “In addition, a fraction of CEMP-no stars might belong to binary systems and have been formed by mass transfer from AGB stars that yielded no s-process elements but enriched carbon (e.g., Suda et al. 2004).”
Evolution of Asymptotic Giant Branch Stars (2005, background): “Suda et al. (2004) propose that the abundance pattern of the currently most metal-poor star—”