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The R-Process Alliance: Fourth Data Release from the Search for R-process-enhanced Stars in the Galactic Halo

Holmbeck, EM; Hansen, TT; Beers, TC; Placco, VM; Whitten, DD; Rasmussen, KC; Roederer, IU; ... Wyse, FG; + view all (2020) The R-Process Alliance: Fourth Data Release from the Search for R-process-enhanced Stars in the Galactic Halo. The Astrophysical Journal Supplement Series , 249 (2) , Article 30. 10.3847/1538-4365/ab9c19. Green open access

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Abstract

This compilation is the fourth data release from the R-Process Alliance (RPA) search for r-process-enhanced stars and the second release based on "snapshot" high-resolution (R ~ 30,000) spectra collected with the du Pont 2.5 m Telescope. In this data release, we propose a new delineation between the r-I and r-II stellar classes at $[\mathrm{Eu}/\mathrm{Fe}]=+0.7$, instead of the empirically chosen $[\mathrm{Eu}/\mathrm{Fe}]=+1.0$ level previously in use, based on statistical tests of the complete set of RPA data released to date. We also statistically justify the minimum level of [Eu/Fe] for definition of the r-I stars, [Eu/Fe] > +0.3. Redefining the separation between r-I and r-II stars will aid in the analysis of the possible progenitors of these two classes of stars and determine whether these signatures arise from separate astrophysical sources at all. Applying this redefinition to previous RPA data, the number of identified r-II and r-I stars changes to 51 and 121, respectively, from the initial set of data releases published thus far. In this data release, we identify 21 new r-II, 111 new r-I (plus 3 re-identified), and 7 new (plus 1 re-identified) limited-r stars out of a total of 232 target stars, resulting in a total sample of 72 new r-II stars, 232 new r-I stars, and 42 new limited-r stars identified by the RPA to date.

Type: Article
Title: The R-Process Alliance: Fourth Data Release from the Search for R-process-enhanced Stars in the Galactic Halo
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/1538-4365/ab9c19
Publisher version: https://doi.org/10.3847/1538-4365/ab9c19
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: Science & Technology, Physical Sciences, Astronomy & Astrophysics, R-process, Nucleosynthesis, Metallicity, Stellar abundances, Population II stars, Stellar atmospheres, NEUTRON-CAPTURE ELEMENTS, RADIAL-VELOCITIES, SURVEY HERES, EVOLUTION, NUCLEOSYNTHESIS, IDENTIFICATION, DISCOVERY, GALAXIES, MODELS, II.
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/10111146
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