The Chemical Composition and Age of the Metal-poor Halo Star BD +17°3248

By J. Cowan, C. Sneden, S. Burles, I. Ivans, Timothy C. Beers, J. Truran, J. E. Lawler, F. Primas, G. Fuller, B. Pfeiffer and 1 more. 2002

254 citations recorded by the source corpus.

We have combined new high-resolution spectra obtained with the Hubble Space Telescope (HST) and ground-based facilities to make a comprehensive new abundance analysis of the metal-poor, halo star BD +17°3248. We have detected the third r-process peak elements osmium, platinum, and (for the first time in a metal-poor star) gold, elements whose abundances can only be reliably determined using HST. Our observations illustrate a pattern seen in other similar halo stars with the abundances of the heavier neutron capture elements, including the third r-process peak elements, consistent with a scaled solar system r-process distribution. The abundances of the lighter neutron capture elements, including germanium and silver, fall below that same scaled solar r-process curve, a result similar to that seen in the ultra-metal-poor star CS 22892-052. A single site with two regimes or sets of conditions, or perhaps two different sites for the lighter and heavier neutron capture elements, might explain the abundance pattern seen in this star. In addition, we have derived a reliable abundance for the radioactive element thorium. We tentatively identify U II at 3859 Å in the spectrum of BD +17°3248, which makes this the second detection of uranium in a very metal-poor halo star. Our combined observations cover the widest range in proton number (from germanium to uranium) thus far of neutron capture elements in metal-poor Galactic halo stars. Employing the thorium and uranium abundances in comparison with each other and with several stable elements, we determine an average cosmochronological age for BD +17°3248 of 13.8 ± 4 Gyr, consistent with that found for other similar metal-poor halo stars.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/2211b05e19632cc3de0e7fe050c8a09cc8fe0c9d

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In Astronomy and Astrophysics

1. C. Sneden
2. Timothy C. Beers
3. Roberto Gallino
4. J. Cowan
5. A. Frebel
6. N. Christlieb
7. Wak Aoki
8. J. Norris

In Instrumentation

1. C. Sneden
2. Timothy C. Beers
3. Roberto Gallino
4. J. Cowan
5. A. Frebel
6. J. Norris
7. E. Carretta
8. Wak Aoki

Citations in the corpus

• The Hamburg/ESO R-process enhanced star survey (HERES) - III. HE 0338-3945 and the formation of the r + s stars (2006, background): “We note that Cowan et al. 2002 find a much lower Ba abundance for this star, which would place it firmly as a r-I star.”
• NEW RARE EARTH ELEMENT ABUNDANCE DISTRIBUTIONS FOR THE SUN AND FIVE r-PROCESS-RICH VERY METAL-POOR STARS (2009, background): “Additional descriptions of these stellar spectra can be found in their original studies: BD+17 3248, Cowan et al. (2002); CS 22892-052, Sneden et al. (2003); HD 115444, Westin et al. (2000); HD 221170, Ivans et al. (2006); see also Cowan et al. (2005).”
• Discovery of HE 1523–0901, a Strongly r-Process-enhanced Metal-poor Star with Detected Uranium (2007, background): “However, one further object is known to exhibit U (V. Hill et al. 2007, in preparation), while for another one, at least a tentative detection has been made (Cowan et al. 2002).”
• Probing the Neutron‐Capture Nucleosynthesis History of Galactic Matter (2002, background): “Recent observations of the spectrum of BD +17o3248 also indicate the presence of uranium, albeit weakly, marking this as the second metal-poor halo star in which U has been detected (Cowan et al. 2002).”
• Neutron star mergers versus core-collapse supernovae as dominant r-process sites in the early Galaxy (2003, background): “…early in galactic evolution and that the r-process is robust for elements heavier than Ba, i.e. originates from a single astrophysical site or at least occurs under well defined physical conditions (e.g. Sneden et al. 2000a; Westin et al. 2000; Cowan et al. 2002; but see also Hill et al. 2002).”
• THE DISCOVERY AND ANALYSIS OF VERY METAL-POOR STARS IN THE GALAXY (2005, background): “THE r-I STARS A handful of r-I stars have been noted in the literature; e.g., HD 115444 (Westin et al. 2000) and BD + 17◦ 3248 (Cowan et al. 2002).”
• Abundance Variations within Globular Clusters (2004, background): “Second, the abundance distribution among the n-capture elements ranges from r-process dominance (characterized by [Eu/Ba] ∼ +1; e.g., Cowan et al. 2002, Hill et al. 2002, Sneden et al. 2003) to s-process dominance ([Eu/Ba] ∼ –1; e.g., Aoki et al. 2002, Lucatello et al. 2003, Van Eck et al. 2003).”
• Neutron-Capture Elements in the Early Galaxy (2008, methodology): “The pink boxes are well-studied r-process-rich stars, including CS 22892-052, HD 115444, CS 31082-001, and BD+17◦3248. that early s-processing could be associated with binary mass transfer.”
• First stars VI - Abundances of C, N, O, Li, and mixing in extremely metal-poor giants. Galactic evolution of the light elements (2004, background): “However, Cowan et al. (2002) conclude, from Strömgren photometry, that the star is indeed highly evolved and the small Hipparcos parallax probably unreliable.”
• The s-Process in Low Metallicity Stars. II. Interpretation of High-Resolution Spectroscopic Observations with AGB models (2011, unknown): “Identified r-I stars are CS 30306– 132 by Honda et al. (2004); Aoki et al. (2005), HD 221170 by Ivans et al. (2006), and BD +173248 by Cowan et al. (2002); Roederer et al. (2010b) ([Eu/Fe] ∼ 0.8 – 0.9).”
• Improved Laboratory Transition Probabilities for Nd II and Application to the Neodymium Abundances of the Sun and Three Metal-poor Stars (2003, methodology): “Nd TRANSITION PROBABILITIES AND ABUNDANCES 561 three stars that we previously studied in detail: HD 115444 (Westin et al. 2000), BD +17 3248 (Cowan et al. 2002), and CS 22892 052 (Sneden et al. 2003).”
• Near-Ultraviolet Observations of HD 221170: New Insights into the Nature of r-Process-rich Stars (2006, methodology): “This ratio is virtually identical to that found for CS 22892-052 (−0.62, Sneden et al. 2003), BD+17◦3248 (−0.51, Cowan et al. 2002) and HD 115444 (−0.60, Westin et al. 2000).”
• Neutron-Capture Elements in the Very Metal Poor Star HD 122563 (2006, methodology): “We adopted the line list used in previous studies for line identifications and analyses of neutron-capture elements (e.g., Hill et al. 2002; Cowan et al. 2002; Sneden et al. 2003; Johnson & Bolte 2004).”
• IMPROVED LABORATORY TRANSITION PROBABILITIES FOR Ce ii, APPLICATION TO THE CERIUM ABUNDANCES OF THE SUN AND FIVE r-PROCESS-RICH, METAL-POOR STARS, AND RARE EARTH LAB DATA SUMMARY (2009, background): “3.3 Cerium Abundances in Five r-Process-Rich Low Metallicity Stars The spectra of several very metal-poor, r-process-rich giant stars were also analyzed to determine their Ce abundances: BD+17º3248 ([Fe/H] = -2.1, [Eu/Fe] = +0.9, Cowan et al. 2002); CS 22892-052 ([Fe/H] = -3.1, [Eu/Fe] = +1.5, Snede”
• The Extremely Metal-poor, Neutron Capture-rich Star CS 22892-052: A Comprehensive Abundance Analysis (2003, methodology): “Construction of atomic/molecular line lists for the synthetic spectra has been described in earlier papers (e.g., Sneden et al. 1996; Westin et al. 2000; Cowan et al. 2002).”