2008MNRAS.387..845J

Using photometric data from the Two-Micron All-Sky Survey (2MASS) and GLIMPSE catalogues, I investigate the incidence of mid-infrared (mid-IR) excesses (∼10µm) in G and K stars of luminosity class III. In order to obtain a large sample size, stars are selected using a near-IR colour-magnitude diagram. Sources which are candidates for showing mid-IR excess are carefully examined and modelled to determined whether they are likely to be G/K giants. It is found that mid-IR excesses are present at a level of (1.8±0.4) x 10^–3. While the origin of these excesses remains uncertain, it is plausible that they arise from debris discs around these stars. I note that the measured incidence is consistent with a scenario in which dust lifetimes in debris discs are determined by Poynting-Robertson drag rather than by collisions.