The R-Process Alliance: Chemical Abundances for a Trio of r-process-enhanced Stars-One Strong, One Moderate, and One Mild

Autor(es):Mostrar menos -

Cain, Madelyn ^{[1, 2]} ; Frebel, Anna ^{[1, 2, 3]} ; Gull, Maude ^{[1, 2]} ; Ji, Alexander P. ^[4] ; Placco, Vinicius M. ^{[5, 3]} ; Beers, Timothy C. ^{[5, 3]} ; Melendez, Jorge ^[6] ; Ezzeddine, Rana ^{[1, 2, 3]} ; Casey, Andrew R. ^[7] ; Hansen, Terese T. ^[4] ; Roederer, Ian U. ^{[8, 3]} ; Sakari, Charli ^{[9, 3]}

Afiliação do(s) autor(es)

^[1] MIT, Dept Phys, Cambridge, MA 02139 - USA

^[2] MIT, Kavli Inst Astrophys & Space Res, 77 Massachusetts Ave, Cambridge, MA 02139 - USA

^[3] Joint Inst Nucl Astrophys, Ctr Evolut Elements, Notre Dame, IN 46556 - USA

^[4] Carnegie Inst Washington Observ, 813 Santa Barbara St, Pasadena, CA 91101 - USA

^[5] Univ Notre Dame, Dept Phys, Notre Dame, IN 46556 - USA

^[6] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, BR-05508900 Sao Paulo, SP - Brazil

^[7] Monash Univ, Sch Phys & Astron, Monash Ctr Astrophys, Melbourne, Vic 3800 - Australia

^[8] Univ Michigan, Dept Astron, Ann Arbor, MI 48109 - USA

^[9] Univ Washington, Dept Astron, Seattle, WA 98195 - USA

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 864, n. 1 SEP 1 2018.
• Citações Web of Science: 2

Resumo

We present detailed chemical abundances of three new bright (V similar to 11), extremely metal-poor ({[}Fe/H]similar to -3.0), r-process- enhanced halo red giants based on high-resolution, high-S/N Magellan/MIKE spectra. We measured abundances for 20-25 neutron- capture elements in each of our stars. J1432-4125 is among the most r-process-rich r-II stars, with {[}Eu/Fe] = +1.44 +/- 0.11. J2005-3057 is an r-I star with {[}Eu/Fe] = +0.94 +/- 0.07. J0858-0809 has {[}Eu/Fe] = +0.23 +/- 0.05 and exhibits a carbon abundance corrected for an evolutionary status of {[}C/Fe] corr = +0.76, thus adding to the small number of known carbon-enhanced r-process stars. All three stars show remarkable agreement with the scaled solar r-rocess pattern for elements above Ba, consistent with enrichment of the birth gas cloud by a neutron star merger. The abundances for Sr, Y, and Zr, however, deviate from the scaled solar pattern. This indicates that more than one distinct r-process site might be responsible for the observed neutron-capture element abundance pattern. Thorium was detected in J1432-4125 and J2005-3057. Age estimates for J1432-4125 and J2005-3057 were adopted from one of two sets of initial production ratios each by assuming the stars are old. This yielded individual ages of 12 +/- 6 Gyr and 10 +/- 6 Gyr, respectively. (AU)

• Processo FAPESP: 12/24392-2 - Espectroscopia de alta precisão: impacto no estudo de planetas, estrelas, a galáxia e cosmologia
• Beneficiário: Jorge Luis Melendez Moreno
• Linha de fomento: Auxílio à Pesquisa - Temático
• Processo FAPESP: 14/18100-4 - Populações estelares na Via Láctea: bojo, halo, disco e regiões de formação de estrelas; instrumentação para espectroscopia de alta resolução
• Beneficiário: Beatriz Leonor Silveira Barbuy
• Linha de fomento: Auxílio à Pesquisa - Temático