IR colors of the Sun from Line-Depth Ratios

We fulfill this requirement by using line-depth ratios to derive in a model-independent way the infrared colors of the Sun, and we use the latter to test the zero point of the Casagrande et al. (Cat. J/A+A/512/A54) effective temperature scale, confirming its accuracy.

Solar colors in the widely used Two Micron All Sky Survey (2MASS) JHK_s_ and WISE W1-4 systems are provided: (V-J)_{sun}_=1.198, (V-H)_{sun}_=1.484, (V-K_s_)_{sun}_=1.560, (J-H)_{sun}_=0.286, (J-K_s_)_{sun}_=0.362, (H-K_s_)_{sun}_=0.076, (V-W1)_{sun}_=1.608, (V-W2)_{sun}_=1.563, (V-W3)_{sun}_=1.552, and (V-W4)_{sun}_=1.604. 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 agrees within the errors, possibly suggesting a 1% offset between the two, thus validating extant near- and mid-infrared absolute calibrations.