The chemical composition of the very metal-poor carbon dwarf G77-61

We have determined the chemical composition of the carbon dwarf G77-61, from Keck IR and optical spectra. We present here a new analysis with the oxygen abundance measured for the first time. We show that G77-61 is extremely metal-poor ([Fe/H] {=} {-}4), with large overabundances of C, N and O ([C/Fe] = 3.2, [N/Fe] = 2.2, [O/Fe] = 2.2). It also shows moderate enhancements of Ca and Mg, Na, and Cr of typically 0.5 dex relative to Fe. We discuss the possible origin of these peculiarities.