DISCOVERY OF SUPER-Li-RICH RED GIANTS IN DWARF SPHEROIDAL GALAXIES

Journal Article · Sun Jun 10 04:00:00 EDT 2012 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/752/1/L16· OSTI ID:22047760

Kirby, Evan N ^[1]; Fu, Xiaoting; Deng, Licai ^[2]; Guhathakurta, Puragra ^[3]

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1. California Institute of Technology, 1200 E. California Blvd., MC 249-17, Pasadena, CA 91125 (United States)
2. Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)
3. University of California Observatories/Lick Observatory, University of California, 1156 High St., Santa Cruz, CA 95064 (United States)

Stars destroy lithium (Li) in their normal evolution. The convective envelopes of evolved red giants reach temperatures of millions of kelvin, hot enough for the {sup 7}Li(p, {alpha}){sup 4}He reaction to burn Li efficiently. Only about 1% of first-ascent red giants more luminous than the luminosity function bump in the red giant branch exhibit A(Li) > 1.5. Nonetheless, Li-rich red giants do exist. We present 15 Li-rich red giants-14 of which are new discoveries-among a sample of 2054 red giants in Milky Way dwarf satellite galaxies. Our sample more than doubles the number of low-mass, metal-poor ([Fe/H] {approx}< -0.7) Li-rich red giants, and it includes the most-metal-poor Li-enhanced star known ([Fe/H] = -2.82, A(Li){sub NLTE} = 3.15). Because most of the stars have Li abundances larger than the universe's primordial value, the Li in these stars must have been created rather than saved from destruction. These Li-rich stars appear like other stars in the same galaxies in every measurable regard other than Li abundance. We consider the possibility that Li enrichment is a universal phase of evolution that affects all stars, and it seems rare only because it is brief.

• OSTI ID: 22047760
• Journal Information: Astrophysical Journal Letters, Journal Name: Astrophysical Journal Letters Journal Issue: 1 Vol. 752; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ALPHA PARTICLES
ASTROPHYSICS
ELEMENT ABUNDANCE
HELIUM 4
HYDROGEN
IRON
LITHIUM
LITHIUM 7 TARGET
LUMINOSITY
MASS
MILKY WAY
PROTON REACTIONS
RED GIANT STARS
STAR EVOLUTION
UNIVERSE