An Elemental Assay of Very, Extremely, and Ultra Metal-Poor Stars

Understand

We present a high-resolution elemental-abundance analysis for a sample of 23 very metal-poor (VMP; [Fe/H] < -2.0) stars, 12 of which are extremely metal-poor (EMP; [Fe/H] < -3.0), and 4 of which are ultra metal-poor (UMP; [Fe/H] < -4.0).

• These stars were targeted to explore differences in the abundance ratios for elements that constrain the possible astrophysical sites of element production, including Li, C, N, O, the alpha-elements, the iron-peak elements, and a number of neutron-capture elements.
• This sample substantially increases the number of known carbon-enhanced metal-poor (CEMP) and nitrogen-enhanced metal-poor (NEMP) stars -- our program stars include eight that are considered &#34;normal&#34; metal-poor stars, six CEMP-no stars, five CEMP-s stars, two CEMP-r stars, and two CEMP-r/s stars.
• One of the CEMP-$r$ stars and one of the CEMP-r/s stars are possible NEMP stars.