Related papers: Neutron-Capture Element Trends in the Halo
The CH star CS 31062-050 ([Fe/H]=-2.42) is one of the most useful stars yet discovered for evaluating the s-process in metal-poor stars. It is very abundant in heavy elements (e.g., [La/Fe]=2.2), and its relatively cool temperature and low…
The heaviest chemical elements are naturally produced by the rapid neutron-capture process (r-process) during neutron star mergers or supernovae. The r-process production of elements heavier than uranium (transuranic nuclei) is poorly…
Abundances for 27 elements in the very metal poor dwarf star HE2148-1247 are presented, including many of the neutron capture elements. We establish that HE2148-1247 is a very highly s-process enhanced star with anomalously high Eu as well,…
The MINCE (Measuring at Intermediate metallicity Neutron-Capture Elements) project aims to gather the abundances of neutron-capture elements but also of light elements and iron peak elements in a large sample of giant stars in this…
The s-process in massive stars, producing nuclei up to $A\approx 90$, has a different behaviour at low metallicity if stellar rotation is significant. This enhanced s-process is distinct from the s-process in massive stars around solar…
Plausible ratios of deuterium to hydrogen D/H as a function of metallicity, time, and redshift are investigated. Guided by the heavy element abundance patterns observed locally in Galactic dwarf stars and at large redshift in quasi-stellar…
We present the results of a detailed abundance analysis of one of the confirmed building blocks of the Milky Way stellar halo, a kinematically-coherent metal-poor stellar stream. We have obtained high resolution and high S/N spectra of 12…
We investigate hydrogen electron capture in the oceans of neutron stars accreting at rates appropriate for most Low-Mass X-Ray Binaries. These stars burn the accreted hydrogen and helium unstably in the upper atmosphere and accumulate…
Knowledge of abundance ratios as functions of metallicity can lead to insights on the origin and evolution of our Galaxy and its stellar populations. We aim to trace the chemical evolution of the neutron-capture elements Sr, Zr, La, Ce, Nd,…
High resolution spectra obtained from the Subaru Telescope High Dispersion Spectrograph have been used to update the stellar atmospheric parameters and metallicity of the star HD 209621. We have derived a metallicity of [Fe/H] = -1.93 for…
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…
Studies of nucleosynthesis in neutrino-driven winds from nascent neutron stars show that the elements from Sr through Ag with mass numbers A~88-110 are produced by charged-particle reactions (CPR) during the alpha-process in the winds.…
New high resolution, very high signal-to-noise spectra of ultra-metal-poor (UMP) giant stars HD 115444 and HD 122563 have been gathered with the High-Resolution Echelle Spectrometer of the McDonald Observatory 2.7m Telescope. With these…
Half of all the elements in the universe heavier than iron were created by rapid neutron capture. The theory for this astrophysical `$r$-process' was worked out six decades ago and requires an enormous neutron flux to make the bulk of these…
The extreme conditions in Neutron Stars make them ideal test facilities for fundamental interactions. A Neutron Star can capture Dark Matter via scattering. As a result of the scattering, Dark Matter kinetic energy is transferred to the…
Some metal-poor stars have abundance patterns which are midway between the slow (s) and rapid (r) neutron capture processes. We show that the helium shell of a fast rotating massive star experiencing a jet-like explosion undergoes two…
We report Sr, Pd and Ag abundances for a sample of metal-poor field giants and analyze a larger sample of Y, Zr, and Ba abundances. The [Y/Zr] and [Pd/Ag] abundance ratios are similar to those measured for the r-process-rich stars CS…
We have made a parametric study of s-process nucleosynthesis in the metal poor ([Fe/H]=-2.7) stars LP625-44 and LP706-7. We find that a high neutron exposure and a small overlap factor are necessary to fit the abundance pattern observed in…
A possible relation between the high dispersion in metallicity of metal-poor halo stars and the minor merger processes in the history of the Galaxy is presented. The foreign populations of stars in the satellites through minor merger…
The astrophysical site(s) of the r-process are uncertain, with candidates such as neutron star mergers and magneto-rotational supernovae predicting different event rates, delay times, and heavy-element yields. Galactic chemical evolution…