Metal-poor Stars Observed with the Automated Planet Finder Telescope. II. Chemodynamical Analysis of Six Low-Metallicity Stars in the Halo System of the Milky Way

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In this work, we study the chemical compositions and kinematic properties of six metal-poor stars with [Fe/H] $< -2.5$ in the Galactic halo.

• From high-resolution (R $\sim$~110,000) spectroscopic observations obtained with the Lick/APF, we determined individual abundances for up to 23 elements, to quantitatively evaluate our sample.
• We identify two carbon-enhanced metal-poor stars (J1630+0953 and J2216+0246) without enhancement in neutron-capture elements (CEMP-no stars), while the rest of our sample stars are carbon-intermediate.
• By comparing the light-element abundances of the CEMP stars with predicted yields from non-rotating zero-metallicity massive-star models, we find that possible the progenitors of J1630+0953 and J2216+0246 could be in the 13-25 M$_{\odot}$ mass range, with explosion energies 0.3-1.8$ \times 10^{51}$ erg.