THE SUPER LITHIUM-RICH RED GIANT RAPID ROTATOR G0928+73.2600: A CASE FOR PLANET ACCRETION?

Journal Article · Mon Nov 01 00:00:00 EDT 2010 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/723/1/L103· OSTI ID:21452705

Carlberg, Joleen K; Majewski, Steven R; Rood, Robert T ^[1]; Smith, Verne V; Cunha, Katia ^[2]

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1. Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)
2. National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)

We present the discovery of a super lithium-rich K giant star, G0928+73.2600. This red giant (T {sub eff} = 4885 K and log g = 2.65) is a fast rotator with a projected rotational velocity of 8.4 km s{sup -1} and an unusually high lithium abundance of A(Li) = 3.30 dex. Although the lack of a measured parallax precludes knowing the exact evolutionary phase, an isochrone-derived estimate of its luminosity places the star on the Hertzsprung-Russell diagram in a location that is not consistent with either the red bump on the first ascent of the red giant branch or with the second ascent on the asymptotic giant branch, the two evolutionary stages where lithium-rich giant stars tend to cluster. Thus, even among the already unusual group of lithium-rich giant stars, G0928+73.2600 is peculiar. Using {sup 12}C/{sup 13}C as a tracer for mixing-more mixing leads to lower {sup 12}C/{sup 13}C-we find {sup 12}C/{sup 13}C = 28, which is near the expected value for standard first dredge-up mixing. We can therefore conclude that 'extra' deep mixing has not occurred. Regardless of the ambiguity of the evolutionary stage, the extremely large lithium abundance and the rotational velocity of this star are unusual, and we speculate that G0928+73.2600 has been enriched in both lithium and angular momentum from a sub-stellar companion.

• OSTI ID: 21452705
• Journal Information: Astrophysical Journal Letters, Vol. 723, Issue 1; Other Information: DOI: 10.1088/2041-8205/723/1/L103; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
ANGULAR MOMENTUM
ASYMPTOTIC SOLUTIONS
CARBON 12
CARBON 13
GIANT STARS
HERTZSPRUNG-RUSSELL DIAGRAM
LITHIUM
LUMINOSITY
PLANETS
ALKALI METALS
CARBON ISOTOPES
DIAGRAMS
ELEMENTS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
INFORMATION
ISOTOPES
LIGHT NUCLEI
MATHEMATICAL SOLUTIONS
METALS
NUCLEI
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
STABLE ISOTOPES
STARS