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M. M. Briley (NSF), A. R. Noll (U. Wisc. Oshkosh)
We present an analysis of a high resolution spectrum of the lithium-rich red giant K301 in the open cluster NGC 7789 as well as an identical treatment of three other "normal" cluster giants. Many scenarios have been put forth to explain the origins of enhanced lithium stars, including the accretion of planets and internal nucelosynthesis. In the present case, our LTE equivalent-width approach based on 90+ Fe I and 10 FeII lines of the three other cluster giants finds an overall metallicity for NGC 7789 of roughly [Fe/H] = -0.1 with no unusual abundance signatures - in accord with results elsewhere in the literature. However, for K301, a model mutually consistent with the average cluster [Fe/H] and the balance between [FeI/H] and [FeII/H] is not possible, e.g., identical abundances from the two ionization states requires an [Fe/H] some 0.4 dex too low. Thus, either K301 is not a member or its atmosphere is not well described by the LTE models. Given radial velocity and proper motion studies available in the literature, it is unlikely that K301 is an interloper. Rather, recent theoretical works on the lithium-flash phenomena include a significant increase in luminosity and rapid expansion driven by the sudden release of energy in the interior. This is also consistent with other evidence in the spectrum of K301, including a strong blue-shifted H-alpha emission feature.
Any opinions, findings, conclusions and recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.