Interferometric measurement of the angular sizes of dwarf stars in the spectral range K3-M4

We have used the Palomar Testbed Interferometer to measure the angular diam eter of five dwarf stars of spectral types K3-M4. Using the 110 m baseline and observing in H and K bands allows us to measure angular diameters with an accuracy of 2%-8% for stars with apparent angular diameters approaching 1 milliarcsecond. We provide results for both uniform-disk and limb-darkene d models and compare our results with theoretical predictions. At the curre nt level of precision our measurements are consistent with most widely acce pted models, but further observations should be able to provide useful empi rical constraints.