Discovery of HE 1523–0901, a Strongly r-Process-enhanced Metal-poor Star with Detected Uranium

By A. Frebel, N. Christlieb, J. Norris, C. Thom, Timothy C. Beers, J. Rhee. 2007

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We present age estimates for the newly discovered, very r-process-enhanced metal-poor star HE 1523-0901 ([Fe/H] = -2.95) based on the radioactive decay of Th and U. The bright (V = 11.1) giant was found among a sample of bright metal-poor stars selected from the Hamburg/ESO Survey. From an abundance analysis of a high-resolution (R = 75,000) VLT/UVES spectrum, we find HE 1523-0901 to be strongly overabundant in r-process elements ([r/Fe] = 1.8). The abundances of heavy neutron-capture elements (Z > 56) measured in HE 1523-0901 match the scaled solar r-process pattern extremely well. We detect the strongest optical U line at 3859.57 Å. For the first time, we are able to employ several different chronometers, such as the U/Th, U/Ir, Th/Eu, and Th/Os ratios to measure the age of a star. The weighted average age of HE 1523-0901 is 13.2 Gyr. Several sources of uncertainties are assessed in detail.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

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Citations in the corpus

Origin of the heaviest elements: The rapid neutron-capture process (2019, background): “, 2006); (f) HD 1523+0157, (Frebel et al., 2007); (g) CS 29491-069, (Hayek et al.”
Stellar Abundances for the Galactic Archeology (SAGA) Database — Compilation of the Characteristics of Known Extremely Metal-Poor Stars (2008, background): “A handful of stars that exhibit large enhancements of the r-process elements (Sneden et al. 1994; Hill et al. 2002; Frebel et al. 2007) have drawn the interest of researchers concerned with nucleosynthesis processes in massive EMP stars and the chemical evolution of the Galaxy.”
The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models (2011, unknown): “…are CS 31082–001 by (Hill et al. 2002; Plez et al. 2004) ([Eu/Fe] ∼ 1.6), HD 115444 by Westin et al. (2000) ([Eu/Fe] = 0.85), HE 1523– 0901 by Frebel et al. (2007) ([Eu/Fe] ∼ 1.8), CS 29497– 004 by Christlieb et al. (2004) ([Eu/Fe] = 1.64), CS 31078– 018 by Lai et al. (2008) ([Eu/Fe] =…”
First stars VIII. Enrichment of the neutron-capture elements in the early Galaxy (2007, unknown): “CS 22892-052, CS 31082-001, the eight new r-II stars found by Barklem et al. (2005), and the most recent discovery HE 1523-0909 (Frebel et al. 2007), all fall in this range.”
Near-Field Cosmology with Extremely Metal-Poor Stars (2015, background): “…supported by the age dating of the rare group of r-process enhanced stars which have ages of 13 – 14Gyr and [Fe/H] ∼ −3.0 (e.g., Hill et al. 2002, Frebel et al. 2007a, Sneden, Cowan & Gallino 2008), it is of critical importance to verify this, by investigating high-redshift early gaseous…”
The stellar halo of the Galaxy (2008, background): “The first measurements of very metal-poor nearby stars have yielded ages of 15.2 ± 3.7 Gyr (Sneden et al. 1996), 14 ± 3 Gyr (Cayrel et al. 2001; Hill et al. 2002), and 13.2 Gyr (Frebel et al. 2007).”
Neutron-Capture Elements in the Early Galaxy (2008, methodology): “…of other r-rich stars have confirmed the same scaled Solar-system abundance pattern for elements with Z ≥ 56 (see, e.g., Westin et al. 2000, Cowan et al. 2002, Hill et al. 2002, Johnson 2002, Johnson & Bolte 2002b, Honda et al. 2004, Barklem et al. 2005, Ivans et al. 2006, Frebel et al. 2007).”
26 Al- 26 Mg and 207 Pb- 206 Pb systematics of Allende CAIs: Canonical solar initial 26 Al/ 27 Al ratio reinstated (2008, methodology): “…themean age of the interstellar dust reservoirs from which CAI AJEF and A43 condensed from, using the following equation (Cayrel et al., 2001; Frebel et al., 2007): TISM ¼ 21:84 log U=Thð Þ0− log U=Thð Þobs ð2Þ where TISM is expressed in Ga (billion years), and (U/Th)0 is the production…”
The s process: Nuclear physics, stellar models, and observations (2010, unknown): “…are labeled r-II by Christlieb et al. (2004), defined as those very metal-poor ([Fe/H] < −2.5) stars with [Eu/Fe] > 1.0 and [Eu/Ba] < 0.0 (e.g., CS 31082-001 by Hill et al. (2002), CS 22183-031 by Honda et al. (2004), HE 1523-0901 by Frebel et al. (2007), CS 29497-004 by Christlieb et al. (2004)).”
SYSTEMATICS OF DYNAMICAL MASS EJECTION, NUCLEOSYNTHESIS, AND RADIOACTIVELY POWERED ELECTROMAGNETIC SIGNALS FROM NEUTRON-STAR MERGERS (2013, background): “…to be relatively robust, in particular in comparison with the Th/Eu chronometry, i.e to be less affected by the still large astrophysics and nuclear physics uncertainties affecting our understanding of the r-process nucleosynthesis (Goriely & Clerbaux 1999; Cayrel et al. 2001; Frebel et al. 2007).”
DETAILED CHEMICAL ABUNDANCES IN THE r-PROCESS-RICH ULTRA-FAINT DWARF GALAXY RETICULUM 2 (2016, methodology): “…have focused on characterizing the r-process abundance pattern in detail (e.g., Sneden et al. 1996, 2003; Hill et al. 2002; Christlieb et al. 2004; Frebel et al. 2007; Siqueira Mello et al. 2013) and modeling the physical conditions of nucleosynthesis to reproduce this pattern (e.g., Wanajo et…”
The Ages of Stars (2007, background): “Another very metal-poor star with enhanced r-process elements, HE 1523–0901, presents a better case, having detectable U (Frebel et al. 2007) and highly consistent ages from both U and Th, with an average of 13.2 Gyr.”