The new record holder for the most iron-poor star: HE 1327−2326, a dwarf or subgiant with [Fe/H] = −5.4

Frebel, A.; Aoki, W.; Christlieb, N.; Ando, H.; Asplund, M.; Barklem, P.S.; Beers, T.C.; Eriksson, K.; Fechner, C.; Fujimoto, M.Y.; Honda, S.; Kajino, T.; Minezaki, T.; Nomoto, K.; Norris, J.E.; Ryan, Sean G.; Takada-Hidai, M.; Tsangarides, S.; Yoshii, Y.

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Author

Frebel, A.

Aoki, W.

Christlieb, N.

Ando, H.

Asplund, M.

Barklem, P.S.

Beers, T.C.

Eriksson, K.

Fechner, C.

Fujimoto, M.Y.

Honda, S.

Kajino, T.

Minezaki, T.

Nomoto, K.

Norris, J.E.

Ryan, Sean G.

Takada-Hidai, M.

Tsangarides, S.

Yoshii, Y.

Abstract

We describe the discovery of HE 1327−2326, a dwarf or subgiant with [Fe/H] = −5.4. The star was found in a sample of bright metal-poor stars selected from the Hamburg/ESO survey. Its abundance pattern is characterized by very high C and N abundances. The detection of Sr which is overabundant by a factor of 10 as compared to iron and the Sun, suggests that neutron-capture elements had already been produced in the very early Galaxy. A puzzling Li depletion is observed in this unevolved star which contradicts the value of the primordial Li derived from WMAP and other Li studies. Possible scenarios for the origin of the abundance pattern (Pop. II or Pop. III) are presented as well as an outlook on future observations.