Abundance Analysis of New $r$-Process-Enhanced Stars from the HESP-GOMPA Survey

TL;DR

This study analyzes the detailed chemical abundances of five new bright $r$-process-enhanced stars from the HESP-GOMPA survey, providing insights into their nucleosynthesis and chemical enrichment histories.

Contribution

It presents the first detailed abundance analysis of five new $r$-process-enhanced stars, including the detection of multiple $r$-process elements and an actinide-boost star, expanding understanding of their origins.

Findings

Detected multiple $r$-process elements in all stars

Identified an actinide-boost star with thorium detection

Compared sub-populations to constrain $r$-process origins

Abstract

We present a study on the detailed chemical abundances of five new relatively bright $r$-process-enhanced stars that were initially observed as part of the SDSS/MARVELS pre-survey. These stars were selected, on the basis of their metallicities and carbon abundances, among a total of 60 stars, for high-resolution spectroscopic follow-up as part of the HESP-GOMPA survey (Hanle Echelle SPectrograph -- Galactic survey Of Metal Poor stArs). Here we discuss the three new $r$-I and two new $r$-II stars found in this survey. We have carried out a detailed abundance analysis for each of these stars, at a resolving power of $R \sim 30,000$, and compare our results to the existing literature. We could measure three of the first $r$-process-peak elements (Sr, Y and Zr) in all five stars, while Ba, Ce, Nd, Sm, Eu, and Dy could be detected among the second $r$-process-peak elements. Thorium could also be detected in one of the targets, which is found to be an actinide-boost star. We have carried out a comparative study among the sub-populations of the $r$-process-enhanced stars and other stars of the Milky Way halo population to constrain the origin of this class of objects. These bright $r$-process-enhanced stars provide an excellent opportunity to study the nucleosynthesis history of this population in great detail, and shed light on their chemical-enrichment histories.