| Full text | |
| Author(s): |
Placco, Vinicius M.
[1, 2]
;
Frebel, Anna
[3, 4]
;
Beers, Timothy C.
[1]
;
Karakas, Amanda I.
[5]
;
Kennedy, Catherine R.
[5]
;
Rossi, Silvia
[2]
;
Christlieb, Norbert
[6]
;
Stancliffe, Richard J.
[7]
Total Authors: 8
|
| Affiliation: | [1] Natl Opt Astron Observ, Tucson, AZ 85719 - USA
[2] Univ Sao Paulo, Dept Astron, Inst Astron Geofis & Ciencias Atmosfer, BR-05508900 Sao Paulo - Brazil
[3] MIT, Cambridge, MA 02139 - USA
[4] Kavli Inst Astrophys & Space Res, Cambridge, MA 02139 - USA
[5] Australian Natl Univ, Res Sch Astron & Astrophys, Weston, ACT 2611 - Australia
[6] Heidelberg Univ, Zentrum Astron, Landessternwarte, D-69117 Heidelberg - Germany
[7] Univ Bonn, Argelander Inst Astron, D-53121 Bonn - Germany
Total Affiliations: 7
|
| Document type: | Journal article |
| Source: | ASTROPHYSICAL JOURNAL; v. 770, n. 2 JUN 20 2013. |
| Web of Science Citations: | 36 |
| Abstract | |
We present a comprehensive abundance analysis of two newly discovered carbon-enhanced metal-poor (CEMP) stars. HE 2138-3336 is a s-process-rich star with {[}Fe/H] = -2.79, and has the highest {[}Pb/Fe] abundance ratio measured thus far, if non-local thermodynamic equilibrium corrections are included ({[}Pb/Fe] = +3.84). HE 2258-6358, with {[}Fe/H] = -2.67, exhibits enrichments in both s- and r-process elements. These stars were selected from a sample of candidate metal-poor stars from the Hamburg/ESO objective-prism survey, and followed up with medium-resolution (R similar to 2000) spectroscopy with GEMINI/GMOS. We report here on derived abundances (or limits) for a total of 34 elements in each star, based on high-resolution (R similar to 30,000) spectroscopy obtained with Magellan-Clay/MIKE. Our results are compared to predictions from new theoretical asymptotic giant branch (AGB) nucleosynthesis models of 1.3 M-circle dot with {[}Fe/H] = -2.5 and -2.8, as well as to a set of AGB models of 1.0 to 6.0 M-circle dot at {[}Fe/H] = -2.3. The agreement with the model predictions suggests that the neutron-capture material in HE 2138-3336 originated from mass transfer from a binary companion star that previously went through the AGB phase, whereas for HE 2258-6358, an additional process has to be taken into account to explain its abundance pattern. We find that a narrow range of progenitor masses (1.0 <= M(M-circle dot) <= 1.3) and metallicities (-2.8 <= {[}Fe/H] <= -2.5) yield the best agreement with our observed elemental abundance patterns. (AU) | |
| FAPESP's process: | 12/13722-1 - (Re)Discovery and analysis of metal-poor stars in the Milky Way |
| Grantee: | Vinicius Moris Placco |
| Support Opportunities: | Scholarships abroad - Research Internship - Post-doctor |
| FAPESP's process: | 10/08996-0 - The Milky Way Halo Revisited |
| Grantee: | Vinicius Moris Placco |
| Support Opportunities: | Scholarships in Brazil - Post-Doctoral |