The infrared colors of the Sun
  Solar infrared colors provide powerful constraints on the stellar effective
temperature scale, but to this purpose they must be measured with both accuracy
and precision. We achieve this requirement by using line-depth ratios to derive
in a model independent way the infrared colors of the Sun, and use the latter
to test the zero-point of the Casagrande et al. (2010) effective temperature
scale, confirming its accuracy. Solar colors in the widely used 2MASS -J H K-
and WISE -W1 W2 W3 W4- systems are provided. A cross check of the effective
temperatures derived implementing 2MASS or WISE magnitudes in the infrared flux
method confirms that the absolute calibration of the two systems agree within
the errors, possibly suggesting a 1% offset between the two, thus validating
extant near and mid infrared absolute calibrations. While 2MASS magnitudes are
usually well suited to derive effective temperatures, we find that a number of
bright, solar-like stars exhibit anomalous WISE colors. In most cases this
effect is spurious and traceable to lower quality measurements, although for a
couple of objects (3 +/- 2 % of the total sample) it might be real and hints
towards the presence of warm/hot debris disks.
