相关论文: The $R$-Process Alliance: Actinide Abundances, Var…

Several extremely metal-poor stars are known to have an enhanced thorium abundance. These actinide-boost stars have likely inherited material from an r-process that operated under different conditions than the most frequent r-process in the…

The r-process production in the early universe has been well constrained by the extensive studies of metal-poor stars. However, the r-process enrichment in the metal-rich regime is still not well understood. In this study, we examine the…

The astrophysical production site of the heaviest elements in the universe remains a mystery. Incorporating heavy element signatures of metal-poor, $r$-process enhanced stars into theoretical studies of $r$-process production can offer…

We examine the Pb and Th abundances in 27 metal-poor stars (-3.1 < [Fe/H] < -1.4) whose very heavy metal (Z > 56) enrichment was produced only by the rapid (r-) nucleosynthesis process. New abundances are derived from HST/STIS, Keck/HIRES,…

We present the abundance analyses for the neutron-capture elements, and discuss the observed abundance distributions in very metal-poor stars with excesses of r-process elements. As has been found by previous abundance studies, the…

We present a nearly complete rapid neutron-capture process (r-process) chemical inventory of the metal-poor ([Fe/H] = -1.46 +/- 0.10) r-process-enhanced ([Eu/Fe] = +1.32 +/- 0.08) halo star HD 222925. This abundance set is the most complete…

We report thorium abundances for 77 metal-poor stars in the metallicity range of -3.5<[Fe/H]}<-1.0, based on "snapshot" spectra obtained with VLT-UT2/UVES during the HERES Survey. We were able to determine the thorium abundances with better…

To better characterize the abundance patterns produced by the r-process, we have derived new abundances or upper limits for the heavy elements zinc (Zn), yttrium (Y), lanthanum (La), europium (Eu), and lead (Pb). Our sample of 161…

We present a detailed abundance analysis of the bright (V = 9.02), metal-poor ([Fe/H] = -1.47 +/- 0.08) field red horizontal-branch star HD 222925, which was observed as part of an ongoing survey by the R-Process Alliance. We calculate…

The ultra-faint dwarf galaxy Reticulum II was enriched by a rare and prolific r-process event, such as a neutron star merger. To investigate the nature of this event, we present high-resolution Magellan/MIKE spectroscopy of the brightest…

Ground- and space-based observations of stellar heavy element abundances are providing a clearer picture of the chemical evolution of the Galaxy. A large number of (r)apid and (s)low neutron capture process elements, including the first…

The chemical abundances of metal-poor stars provide important clues to explore stellar formation history and set significant constraints on models of the r-process. In this work, we find that the abundance patterns of the light and iron…

From newly-obtained high-resolution, high signal-to-noise ratio spectra the abundances of the elements La and Eu have been determined over the stellar metallicity range -3<[Fe/H]<+0.3 in 159 giant and dwarf stars. Lanthanum is predominantly…

There has been a concerted effort in recent years to identify the astrophysical sites of the $r$-process that can operate early in the Galaxy. The discovery of many $r$-process-enhanced (RPE) stars (especially by the $R$-process Alliance…

The rapid neutron capture or 'r process' of nucleosynthesis is believed to be responsible for the production of approximately half the natural abundance of heavy elements found on the periodic table above iron (with proton number $Z=26$)…

The astrophysical origin of the rapid neutron-capture process (r-process), which produces about half of the elements heavier than iron, remains uncertain. The oldest, most metal-poor stars preserve the chemical signatures of early…

Of the variations in the elemental abundance patterns of stars enhanced with $r$-process elements, the variation in the relative actinide-to-lanthanide ratio is among the most significant. We investigate the source of these actinide…

The study of the origin of heavy elements is one of the main goals of nuclear astrophysics. In this paper, we present new observational data for the heavy $r$-process elements gadolinium (Gd, Z=64), dysprosium (Dy, Z=66) and thorium (Th,…

Understanding the abundance pattern of metal-poor stars and the production of heavy elements through various nucleosynthesis processes offers crucial insights into the chemical evolution of the Milky Way, revealing primary sites and major…

We present and discuss three extremely r-process enhanced stars located in the massive dwarf spheriodal galaxy Fornax. These stars are very unique with an extreme Eu enrichment ($1.25\le \mathrm{[Eu/Fe]} \le 1.45$) at high metallicities…