An <i>r</i>-process Enhanced Star in the Dwarf Galaxy Tucana III

Hansen, T. T.; Simon, J. D.; Marshall, J. L.; Li, T. S.; Carollo, D.; DePoy, D. L.; Nagasawa, D. Q.; Bernstein, R. A.; Drlica-Wagner, A.; Abdalla, F. B.; Allam, S.; Annis, J.; Bechtol, K.; Benoit-Levy, A.; Brooks, D.; Buckley-Geer, E.; Carnero Rosell, A.; Kind, M. Carrasco; Carretero, J.; Cunha, C. E.; da Costa, L. N.; Desai, S.; Eifler, T. F.; Fausti Neto, A.; Flaugher, B.; Frieman, J.; Garcia-Bellido, J.; Gaztanaga, E.; Gerdes, D. W.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutierrez, G.; James, D. J.; Krause, E.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Miquel, R.; Plazas, A. A.; Romer, A. K.; Sanchez, E.; Santiago, B.; Scarpine, V.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Walker, A. R.; DES Collaboration
2017
ASTROPHYSICAL JOURNAL
DOI
10.3847/1538-4357/aa634a
Chemically peculiar stars in dwarf galaxies provide a window for exploring the birth environment of stars with varying chemical enrichment. We present a chemical abundance analysis of the brightest star in the newly discovered ultra-faint dwarf galaxy candidate Tucana III. Because it is particularly bright for a star in an ultra-faint Milky Way (MW) satellite, we are able to measure the abundance of 28 elements, including 13 neutron-capture species. This star, DES. J235532.66-593114.9 (DES J235532), shows a mild enhancement in neutron-capture elements associated with the r-process and can be classified as an r-I star. DES. J235532 is the first r-I star to be discovered in an ultra-faint satellite, and Tuc. III is the second extremely low-luminosity system found to contain r-process enriched material, after Reticulum. II. Comparison of the abundance pattern of DES. J235532 with r-I and r-II stars found in other dwarf galaxies and in the MW halo suggests a common astrophysical origin for the neutron-capture elements seen in all r-process enhanced stars. We explore both internal and external scenarios for the r-process enrichment of Tuc. III and show that with abundance patterns for additional stars, it should be possible to distinguish between them.