Detection of Elements at All Three r-process Peaks in the Metal-Poor Star HD 160617

TL;DR

This study reports the first detection of elements at all three r-process peaks in a metal-poor star, including arsenic and selenium, providing new insights into nucleosynthesis processes in the early universe.

Contribution

It presents the first detection of arsenic and selenium in a halo star and provides comprehensive abundance measurements for 45 elements, including all three r-process peaks.

Findings

Detection of arsenic and selenium in a halo star.

Abundances of r-process elements align with solar system predictions.

Surprising similarity in light and heavy r-process element production.

Abstract

We report the first detection of elements at all three r-process peaks in the metal-poor halo star HD 160617. These elements include arsenic and selenium, which have not been detected previously in halo stars, and the elements tellurium, osmium, iridium, and platinum, which have been detected previously. Absorption lines of these elements are found in archive observations made with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. We present up-to-date absolute atomic transition probabilities and complete line component patterns for these elements. Additional archival spectra of this star from several ground-based instruments allow us to derive abundances or upper limits of 45 elements in HD 160617, including 27 elements produced by neutron-capture reactions. The average abundances of the elements at the three r-process peaks are similar to the predicted solar system r-process residuals when scaled to the abundances in the rare earth element domain. This result for arsenic and selenium may be surprising in light of predictions that the production of the lightest r-process elements generally should be decoupled from the heavier r-process elements.