The super lithium-rich red giant rapid rotator g0928+73.2600: A case for planet accretion?

Joleen K. Carlberg, Verne V. Smith, Katia Cunha, Steven R. Majewski, Robert T. Rood

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

We present the discovery of a super lithium-rich K giant star, G0928+73.2600. This red giant (Teff = 4885 K and log g = 2.65) is a fast rotator with a projected rotational velocity of 8.4 km s-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 lithiumrich giant stars tend to cluster. Thus, even among the already unusual group of lithium-rich giant stars, G0928+73.2600 is peculiar. Using 12C/ 13C as a tracer for mixing-more mixing leads to lower 12C/13C-we find 12C/13C = 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.

Original languageEnglish (US)
Pages (from-to)L103-L107
JournalAstrophysical Journal Letters
Volume723
Issue number1 PART 2
DOIs
StatePublished - Nov 1 2010
Externally publishedYes

Keywords

  • Stars: abundances
  • Stars: chemically peculiar
  • Stars: rotation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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