Infrared flux method and colour calibrations

The Infrared Flux Method (IRFM) is one of the most accurate techniques to derive fundamental stellar parameters - namely effective temperatures, bolometric luminosities and angular diameters - in an almost model independent way. We review the method and its application to late-type dwarfs, with particular emphasis on the dependence of the resulting effective temperatures on the adopted absolute calibration. We also compare our results with a large set of recent interferometric angular diameters in order to better constrain the temperature scale: despite the excellent agreement we find, uncertainties of order 100 K cannot yet be ruled out. We conclude that although such disturbing uncertainty still plagues the determination of accurate effective temperatures, the homogeneous and internally precise fundamental stellar parameters determined via IRFM permit the study of the fine structure of the lower main sequence in greater detail than ever before.