Search

We present a comprehensive analysis of the detailed chemical abundances for a sample of 11 metal-poor, very metal-poor, and extremely metal-poor stars ([Fe/H] = −1.65 to [Fe/H]  = −3.0) as part of the HESP-GOMPA (Galactic survey Of Metal Poor stArs) survey. The abundance determinations encompass a range of elements, including C, Na, Mg, Al, Si, Ca, Sc, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, and Ba, with a subset of the brighter objects allowing for the measurement of additional key elements. Notably, the abundance analysis of a relatively bright highly r -process-enhanced (r -II) star (SDSS J0019+3141) exhibits a predominantly main r -process signature and variations in the lighter r -process elements. Moreover, successful measurements of thorium in this star facilitate stellar age determinations. We find a consistent odd–even nucleosynthesis pattern in these stars, aligning with expectations for their respective metallicity levels, thus implicating Type II supernovae as potential progenitors. From the interplay between the light and heavy r -process elements, we infer a diminishing relative production of light r -process elements with increasing Type II supernova contributions, challenging the notion that Type II supernovae are the primary source of these light r -process elements in the early Milky Way. A chemodynamical analysis based on Gaia astrometric data and our derived abundances indicates that all but one of our program stars are likely to be of accreted origin. Additionally, our examination of α-poor stars underscores the occurrence of an early accretion event from a satellite on a prograde orbit, similar to that of the Galactic disc. [ABSTRACT FROM AUTHOR]

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 ∼ 30,000, and we 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 subpopulations 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. [ABSTRACT FROM AUTHOR]