The chemical abundance pattern of the extremely metal-poor thin disk star 2MASS J1808-5104 and its origins

Understand

We present a high-resolution ($R\sim35,000$), high signal-to-noise ($S/N=350$) Magellan/MIKE spectrum of the bright extremely metal-poor star 2MASS~J1808$-$5104.

• We find [Fe/H] = $-$4.01 (spectroscopic LTE stellar parameters), [Fe/H] = $-$3.8 (photometric stellar parameters), [Fe/H] = $-$3.7 (spectroscopic NLTE stellar parameters).
• We measured a carbon-to-iron ratio of $\mbox{[C/Fe]}= 0.38$ from the CH G-band.
• J1808$-$5104 is thus not carbon-enhanced, contrary to many other stars with similarly low iron abundances.