Near-Ultraviolet Observations of HD 221170: New Insights into the Nature of r-Process-rich Stars

By I. Ivans, J. Simmerer, C. Sneden, J. E. Lawler, J. Cowan, Roberto Gallino, S. Bisterzo. 2006

184 citations recorded by the source corpus.

Employing high-resolution spectra obtained with the near-UV-sensitive detector on the Keck I HIRES, supplemented by data obtained with the McDonald Observatory 2d-coudé, we have performed a comprehensive chemical composition analysis of the bright r-process-rich metal-poor red giant star HD 221170. Analysis of 57 individual neutral and ionized species yielded abundances for a total of 46 elements and significant upper limits for an additional five. Model stellar atmosphere parameters were derived with the aid of ~200 Fe peak transitions. From more than 350 transitions of 35 neutron-capture (Z > 30) species, abundances for 30 neutron-capture elements and upper limits for three others were derived. Utilizing 36 transitions of La, 16 of Eu, and seven of Th, we derive ratios of log ϵ(Th/La) = -0.73 (σ = 0.06) and log ϵ(Th/Eu) = -0.60 (σ = 0.05), values in excellent agreement with those previously derived for other r-process-rich metal-poor stars such as CS 22892-052, BD +17 3248, and HD 115444. Based on the Th/Eu chronometer, the inferred age is 11.7 ± 2.8 Gyr. The abundance distribution of the heavier neutron-capture elements (Z ≥ 56) is fitted well by the predicted scaled solar system r-process abundances, as also seen in other r-process-rich stars. Unlike other r-process-rich stars, however, we find that the abundances of the lighter neutron-capture elements (37 < Z < 56) in HD 221170 are also in agreement with the abundances predicted for the scaled solar r-process pattern.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/61dcb994371d1d1192bbd3d1623b0708d8083599

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In Astronomy and Astrophysics

1. C. Sneden
2. J. Cowan
3. Roberto Gallino
4. Timothy C. Beers
5. M. Walker
6. J. E. Lawler
7. I. Ivans
8. J. Simon

In Instrumentation

1. C. Sneden
2. J. Cowan
3. M. Walker
4. Roberto Gallino
5. Timothy C. Beers
6. J. Simon
7. M. Geha
8. J. E. Lawler

Citations in the corpus

• 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 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, methodology): “…[Eu/Fe] = +0.9, Cowan et al. 2002); CS 22892-052 ([Fe/H] = -3.1, [Eu/Fe] = +1.5, Sneden et al. 2003a); CS 31082-001 ([Fe/H] = -2.9, [Eu/Fe] = +1.7, Hill et al. 2002); HD 115444 ([Fe/H] = -2.9, [Eu/Fe] = +0.8, Westin et al. 2000); and HD 221170 ([Fe/H] = -2.2, [Eu/Fe] = +0.8, Ivans et al. 2006).”
• 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).”
• Where, oh where has the r-process gone? (2007, methodology): “Figure 7a shows the data on CS 22892–052 with [Fe/H] = −3.1 [black squares (Sneden et al., 2003)] and the recent results on HD 221170 with [Fe/H] = −2.2 [blue squares (Ivans et al., 2006)].”
• HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: URSA MAJOR II and COMA BERENICES (2009, methodology): “For the measurements of atomic absorption lines we employ a line list based on the compilations of Aoki et al. (2007b) and Ivans et al. (2006).”
• Origin of the heaviest elements: The rapid neutron-capture process (2019, background): “, 2013); (e) HD 221170, (Ivans et al., 2006); (f) HD 1523+0157, (Frebel et al.”
• Nucleosynthesis in the Early Galaxy (2007, background): “Also included is the abundance pattern in the moderately r-element enhanced star HD 221170 (Ivans et al. 2006) which does not exhibit the underabundance of light r-process elements with respect to the solar rprocess contribution.”
• THE ABUNDANCES OF NEUTRON-CAPTURE SPECIES IN THE VERY METAL-POOR GLOBULAR CLUSTER M15: A UNIFORM ANALYSIS OF RED GIANT BRANCH AND RED HORIZONTAL BRANCH STARS (2011, unknown): “…et al. 2008](91); HD 115444 [Westin et al. 2000(97), Sneden et al. 2009(87)]; HD 122563 [Cowan et al. 2005(23), Lai et al. 2007(60)]; HD 221170 [Ivans et al. 2006(49), Sneden et 9B028, B412, and B584 are not included in the figure as these stars lack abundances for most of the elements in the…”
• DETAILED CHEMICAL ABUNDANCES IN THE r-PROCESS-RICH ULTRA-FAINT DWARF GALAXY RETICULUM 2 (2016, methodology): “…2005; (18) Wickliffe et al. 1994; (19) Kramida et al. 2015, using HFS/IS from McWilliam 1998 when available; (20) Lawler et al. 2001a, using HFS from Ivans et al. 2006; (21) Lawler et al. 2009; (22) Li et al. 2007, using HFS from Sneden et al. 2009; (23) Ivarsson et al. 2001, using HFS from…”
• 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).”
• HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS FROM SDSS/SEGUE. I. ATMOSPHERIC PARAMETERS AND CHEMICAL COMPOSITIONS (2012, unknown): “…0.000 20 Y II 4374.935 0.160 0.409 21 Y II 4854.863 −0.380 0.992 21 Y II 4883.685 0.070 1.084 21 Y II 4900.110 −0.090 1.030 21 Ba II 4554.029 0.163 0.000 22 Ba II 4934.076 −0.150 0.000 1 Ba II 5853.690 −0.910 0.600 6 Ba II 6141.730 −0.080 0.700 6 Ba II 6496.910 −0.380 0.600 6 La II 4086.709 −0.070…”