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arXiv · 1904.07471

The lowest detected stellar Fe abundance: The halo star SMSS J160540.18-144323.1

T. Nordlander·M. S. Bessell·G. S. Da Costa·A. D. Mackey·M. Asplund·A. R. Casey·A. Chiti·R. Ezzeddine·A. Frebel·K. Lind·A. F. Marino·S. J. Murphy·J. E. Norris·B. P. Schmidt·D. Yong
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Abstract

We report the discovery of SMSS J160540.18-144323.1, a new ultra-metal poor halo star discovered with the SkyMapper telescope. We measure [Fe/H] = -6.2 +- 0.2 (1D LTE), the lowest ever detected abundance of iron in a star. The star is strongly carbon-enhanced, [C/Fe] = 3.9 +- 0.2, while other abundances are compatible with an alpha-enhanced solar-like pattern with [Ca/Fe] = 0.4 +- 0.2, [Mg/Fe] = 0.6 +- 0.2, [Ti/Fe] = 0.8 +- 0.2, and no significant s- or r-process enrichment, [Sr/Fe] < 0.2 and [Ba/Fe] < 1.0 (3{\sigma} limits). Population III stars exploding as fallback supernovae may explain both the strong carbon enhancement and the apparent lack of enhancement of odd-Z and neutron-capture element abundances. Grids of supernova models computed for metal-free progenitor stars yield good matches for stars of about 10 solar mass imparting a low kinetic energy on the supernova ejecta, while models for stars more massive than roughly 20 solar mass are incompatible with the observed abundance pattern.

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T. Nordlander, M. S. Bessell, G. S. Da Costa, A. D. Mackey, M. Asplund, A. R. Casey, A. Chiti, R. Ezzeddine, A. Frebel, K. Lind, A. F. Marino, S. J. Murphy, J. E. Norris, B. P. Schmidt, D. Yong. 2019-04-16. The lowest detected stellar Fe abundance: The halo star SMSS J160540.18-144323.1. https://doi.org/10.1093/mnrasl%2Fslz109

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