Sakari, CM;
Placco, VM;
Farrell, EM;
Roederer, IU;
Wallerstein, G;
Beers, TC;
Ezzeddine, R;
... Watson, F; + view all
(2018)
The R-Process Alliance: First Release from the Northern Search for r-process-enhanced Metal-poor Stars in the Galactic Halo.
The Astrophysical Journal
, 868
(2)
, Article 110. 10.3847/1538-4357/aae9df.
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Abstract
This paper presents the detailed abundances and r-process classifications of 126 newly identified metal-poor stars as part of an ongoing collaboration, the R-Process Alliance. The stars were identified as metal-poor candidates from the RAdial Velocity Experiment (RAVE) and were followed up at high spectral resolution (R ~ 31,500) with the 3.5 m telescope at Apache Point Observatory. The atmospheric parameters were determined spectroscopically from Fe i lines, taking into account $\langle 3{\rm{D}}\rangle $ non-LTE corrections and using differential abundances with respect to a set of standards. Of the 126 new stars, 124 have [Fe/H] < −1.5, 105 have [Fe/H] < −2.0, and 4 have [Fe/H] < −3.0. Nine new carbon-enhanced metal-poor stars have been discovered, three of which are enhanced in r-process elements. Abundances of neutron-capture elements reveal 60 new r-I stars (with +0.3 ≤ [Eu/Fe] ≤ +1.0 and [Ba/Eu] < 0) and 4 new r-II stars (with [Eu/Fe] > +1.0). Nineteen stars are found to exhibit a "limited-r" signature ([Sr/Ba] > +0.5, [Ba/Eu] < 0). For the r-II stars, the second- and third-peak main r-process patterns are consistent with the r-process signature in other metal-poor stars and the Sun. The abundances of the light, α, and Fe-peak elements match those of typical Milky Way (MW) halo stars, except for one r-I star that has high Na and low Mg, characteristic of globular cluster stars. Parallaxes and proper motions from the second Gaia data release yield UVW space velocities for these stars that are consistent with membership in the MW halo. Intriguingly, all r-II and the majority of r-I stars have retrograde orbits, which may indicate an accretion origin.
| Type: | Article |
|---|---|
| Title: | The R-Process Alliance: First Release from the Northern Search for r-process-enhanced Metal-poor Stars in the Galactic Halo |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.3847/1538-4357/aae9df |
| Publisher version: | https://doi.org/10.3847/1538-4357/aae9df |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | Galaxy: formation; stars: abundances; stars: atmospheres; stars: fundamental parameters |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10064876 |
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