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

Abstract

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.

Authors:
 [1]; ;  [2];  [3]
  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)
Publication Date:
OSTI Identifier:
22047760
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal Letters
Additional Journal Information:
Journal Volume: 752; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 2041-8205
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; 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

Citation Formats

Kirby, Evan N., Fu, Xiaoting, Deng, Licai, and Guhathakurta, Puragra. DISCOVERY OF SUPER-Li-RICH RED GIANTS IN DWARF SPHEROIDAL GALAXIES. United States: N. p., 2012. Web. doi:10.1088/2041-8205/752/1/L16.
Kirby, Evan N., Fu, Xiaoting, Deng, Licai, & Guhathakurta, Puragra. DISCOVERY OF SUPER-Li-RICH RED GIANTS IN DWARF SPHEROIDAL GALAXIES. United States. doi:10.1088/2041-8205/752/1/L16.
Kirby, Evan N., Fu, Xiaoting, Deng, Licai, and Guhathakurta, Puragra. Sun . "DISCOVERY OF SUPER-Li-RICH RED GIANTS IN DWARF SPHEROIDAL GALAXIES". United States. doi:10.1088/2041-8205/752/1/L16.
@article{osti_22047760,
title = {DISCOVERY OF SUPER-Li-RICH RED GIANTS IN DWARF SPHEROIDAL GALAXIES},
author = {Kirby, Evan N. and Fu, Xiaoting and Deng, Licai and Guhathakurta, Puragra},
abstractNote = {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.},
doi = {10.1088/2041-8205/752/1/L16},
journal = {Astrophysical Journal Letters},
issn = {2041-8205},
number = 1,
volume = 752,
place = {United States},
year = {2012},
month = {6}
}