| Abstract: | As stars evolve from the main-sequence (MS) to the red giant branch (RGB) they exhibit several characteristic changes -- as the outer layers expand and cool, the star's rotation rate slows, the convection zone deepens and a series of shell-burning and core-burning phases begin to take place. A number of RGB K-type stars, however, exhibit uncharacteristically rapid rotation rates that also seem to be correlated with high lithium abundances (Carlberg et al. 2012). These higher rotation rates and Li abundances are inconsistent with those predicted by standard stellar evolutionary models. It has also been suggested that many of these high-Li RGB stars have IRAS excesses suggestive of a circumstellar shell or disk (de la Reza et al. 1997, Drake et al. 2002). Various hypotheses have been proposed to explain the Li, rapid rotation rates and IR excesses, including the accretion of nearby giant planets equivalent to a few Jupiter masses or a newly triggered nuclear fusion stage that could eject a dusty shell. Using higher spatial resolution data from WISE, we have reevaluated these IRAS-selected targets and included a much larger sample of RGB K-type giants from Carlberg et al. (2012) that were selected without regard to IR brightness. Our findings indicate that many of the IRAS sources that exhibited an IR excess before and were used to support this model are, in fact, non-stellar objects, clusters of stars or galaxies, or otherwise not likely RGB stars, casting doubt on the correlations found previously. Very few of the Carlberg et al. sample have IR excesses, making it difficult to assess if there is a correlation in this sample. This research was conducted as part of the NASA/IPAC Teacher Archive Research Project (NITARP). |