Chemical Analysis of the Brightest Star of the Cetus II Ultrafaint Dwarf Galaxy Candidate

Webber, K. B.; Hansen, T. T.; Marshall, J. L.; Simon, J. D.; Pace, A. B.; Mutlu-Pakdil, B.; Drlica-Wagner, A.; Martínez-Vázquez, C. E.; Aguena, M.; Allam, S. S.; Alves, O.; Bertin, E.; Brooks, D.; Carnero Rosell, A.; Carretero, J.; da Costa, L. N.; De Vicente, J.; Doel, P.; Ferrero, I.; Friedel, D.; Frieman, J.; García-Bellido, J.; Giannini, G.; Gruen, D.; Gruendl, R. A.; Hinton, S. R.; Hollowood, D. L.; Honscheid, K.; Kuehn, K.; Mena-Fernández, J.; Menanteau, F.; Miquel, R.; Ogando, R. L. C.; Pereira, M. E. S.; Pieres, A.; Plazas Malagón, A. A.; Sanchez, E.; Santiago, B.; Smith, J. Allyn; Smith, M.; Suchyta, E.; Tarle, G.; To, C.; Weaverdyck, N.; Yanny, B.
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The Astrophysical Journal

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We present a detailed chemical abundance analysis of the brightest star in the ultrafaint dwarf (UFD) galaxy candidate Cetus II from high-resolution Magellan/MIKE spectra. For this star, DES J011740.53-173053, abundances or upper limits of 18 elements from carbon to europium are derived. Its chemical abundances generally follow those of other UFD galaxy stars, with a slight enhancement of the α-elements (Mg, Si, and Ca) and low neutron-capture element (Sr, Ba, and Eu) abundances supporting the classification of Cetus II as a likely UFD. The star exhibits lower Sc, Ti, and V abundances than Milky Way (MW) halo stars with similar metallicity. This signature is consistent with yields from a supernova originating from a star with a mass of ~11.2 M ⊙. In addition, the star has a potassium abundance of [K/Fe] = 0.81, which is somewhat higher than the K abundances of MW halo stars with similar metallicity, a signature that is also present in a number of UFD galaxies. A comparison including globular clusters and stellar stream stars suggests that high K is a specific characteristic of some UFD galaxy stars and can thus be used to help classify objects as UFD galaxies. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.
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