Actinide-rich and Actinide-poor r-process-enhanced Metal-poor Stars Do Not Require Separate r-process Progenitors by Holmbeck, Erika M., Frebel, Anna L., McLaughlin, G. C., Mumpower, Matthew R., Sprouse, Trevor M., Surman, Rebecca

“…In this study, we introduce and apply the "actinide-dilution with matching" model to a variety of stellar groups, ranging from actinide-deficient to actinide-enhanced, to empirically characterize r-process ejecta mass as a function of electron fraction. …”
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From Actinides to Zinc: Using the Full Abundance Pattern of the Brightest Star in Reticulum II to Distinguish between Different by Ji, Alexander P., Frebel, Anna L.

“…The high signal-to-noise allows us to determine the abundances of 41 elements, including the radioactive actinide element Th and first ever detections of third r-process peak elements (Os and Ir) in a star outside the Milky Way. …”
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RAVE J203843.2–002333: The First Highly R-process-enhanced Star Identified in the RAVE Survey by Placco, Vinicius M., Holmbeck, Erika M., Beers, Timothy C., Surman, Rebecca A., Points, Sean D., Kaleida, Catherine C., Hansen, Terese T., Sakari, Charli M., Casey, Andrew R., Frebel, Anna L., Ji, Alexander Pung, Ezzeddine, Rana

“…The derived chemical abundance pattern exhibits good agreement with those of other known highly r-process-enhanced stars, and evidence suggests that it is not an actinide-boost star. Age estimates were calculated using U/X abundance ratios, yielding a mean age of 13.0 ± 1.1 Gyr.…”
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The r-process Pattern of a Bright, Highly r -process-enhanced Metal-poor Halo Star at [Fe/H ] ~ -2 by Sakari, Charli M., Placco, Vinicius M., Hansen, Terese, Holmbeck, Erika M., Beers, Timothy C., Roederer, Ian U., Venn, Kim A., Wallerstein, George, Davis, Christopher Evan, Farrell, Elizabeth M., Yong, David, Frebel, Anna L.

“…As with many other r-process-enhanced stars, J1538-1804's r-process pattern matches that of the Sun for elements between the first, second, and third peaks, and does not exhibit an actinide boost. Cosmo-chronometric age-dating reveals the r-process material to be quite old. …”
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