  Infrared (IR) excesses around K-type red giants (RGs) have previously been
discovered using IRAS data, and past studies have suggested a link between RGs
with overabundant Li and IR excesses, implying the ejection of circumstellar
shells or disks. We revisit the question of IR excesses around RGs using higher
spatial resolution IR data, primarily from WISE. Our goal was to elucidate the
link between three unusual RG properties: fast rotation, enriched Li, and IR
excess. We have 316 targets thought to be K giants, about 40% of which we take
to be Li-rich. In 24 cases with previous detections of IR excess at low spatial
resolution, we believe that source confusion is playing a role, in that either
(a) the source that is bright in the optical is not responsible for the IR
flux, or (b) there is more than one source responsible for the IR flux as
measured in IRAS. We looked for IR excesses in the remaining sources,
identifying 28 that have significant IR excesses by ~20 um (with possible
excesses for 2 additional sources). There appears to be an intriguing
correlation in that the largest IR excesses are all in Li-rich K giants, though
very few Li-rich K giants have IR excesses (large or small). These largest IR
excesses also tend to be found in the fastest rotators. There is no correlation
of IR excess with the carbon isotopic ratio, 12C/13C. IR excesses by 20 um,
though relatively rare, are at least twice as common among our sample of
Li-rich K giants. If dust shell production is a common by-product of Li
enrichment mechanisms, these observations suggest that the IR excess stage is
very short-lived, which is supported by theoretical calculations. Conversely,
the Li-enrichment mechanism may only occasionally produce dust, and an
additional parameter (e.g., rotation) may control whether or not a shell is
ejected.
