Abstract The ages of the oldest and most metal-poor stars in Milky Way bear important information on age universe its standard model. We analyze a sample 28 extremely field solar vicinity culled from literature carefully determine their ages. To this aim, we critically make use Gaia data to derive distances associated uncertainties. Particular attention has been paid estimate reddening effect d...

Abstract The abundances of r -process elements very metal-poor stars capture the history enrichment in early stage star formation a galaxy. Currently, various types astrophysical sites including neutron mergers (NSMs), magneto-rotational supernovae, and collapsars, are suggested as origin elements. time delay between production is key to distinguish these scenarios, with caveat that diffusion i...

Abstract We have derived new detailed abundances of Mg, Ca, and the Fe-group elements Sc through Zn ( Z = 21−30) for 37 main-sequence turnoff very metal-poor stars ([Fe/H] ≲−2.1). analyzed Keck HIRES optical near-UV high signal-to-noise spectra originally gathered a Be abundance survey. Using typically ∼400 lines with accurate laboratory transition probabilities each star, we determined LTE met...