Hertzsprung-Russell diagram where we highlight sources with the label “binary” or “XRB” (X-ray binary) in Bonanos et al. (2010) (B10), and sources that show emission features. Emission features can be indicated by spectral type information in the B10 catalog, or by an infrared color larger than J − [3.6] = 0.5 mag in B10. This figure contains slightly fewer sources than for example Fig. 5 because it only shows those that have both a known J and [3.6] magnitude.