期刊
ASTROPHYSICAL JOURNAL LETTERS
卷 697, 期 1, 页码 L63-L67出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/697/1/L63
关键词
Galaxy: halo; stars: abundances; stars: Population II; supernovae: general
资金
- National Science Foundation [AST-0802292, AST-0098617, AST-0607770, PHY 02-16783, HY 08-22648]
- Physics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA)
- UK Space Agency [PP/D006570/1] Funding Source: researchfish
As part of a program to measure abundance ratios in stars beyond 15 kpc from the Galactic center, we have discovered a metal-poor star in the outer halo with a unique chemical signature. We originally identified it in the Sloan Extension for Galactic Understanding and Exploration survey as a distant metal-poor star. We obtained a follow-up spectrum using the Echelle Spectrometer and Imager at the Keck 2 telescope, and measure [Fe/H] = -3.17, [Mg/Fe]= -0.10, and [Ca/Fe] = +1.11. This is one of the largest over-abundances of Ca measured in any star to date; the extremely low value of [Mg/Ca] = -1.21 is entirely unique. To have found such an unusual star in our small sample of 27 targets suggests that there may be previously unobserved classes of stars yet to be found in situ in the Galactic halo.
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