Discovery of HE 1523-0901, a strongly r-process-enhanced metal-poor star with detected uranium

• We present age estimates for the newly discovered, very r-process-enhanced metal-poor star HE 1523 - 0901 ([Fe/H] = -2.95) based on the radioactive decay of Th and U. The bright (V = 11.1) giant was found among a sample of bright metal-poor stars selected from the Hamburg/ESO Survey. From an abundance analysis of a high-resolution (R = 75,000) VLT/UVES spectrum, we find HE 1523 - 0901 to be strongly overabundant in r- process elements ([r/Fe] = 1.8). The abundances of heavy neutron-capture elements (Z > 56) measured in HE 1523 - 0901 match the scaled solar r- process pattern extremely well. We detect the strongest optical U line at 3859.57 angstrom. For the first time, we are able to employ several different chronometers, such as the U/Th, U/Ir, Th/ Eu, and Th/Os ratios to measure the age of a star. The weighted average age of HE 1523 - 0901 is 13.2 Gyr. Several sources of uncertainties are assessed in detail.

Ämnesord

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

Nyckelord

early universe

Galaxy : halo

nuclear reactions

nucleosynthesis

abundances

stars : abundances

stars : individual (HE 1523-0901)

Physics

Fysik

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