Accurate and Precise Effective Temperatures for Cool Stars

There is an urgent need for benchmark stars with effective temperature measurements that are both accurate and precise. There are few standard stars currently available with effective temperature measurements that meet the required accuracy for calibrating temperature indicators for cool dwarf stars (+/- 50K or better). We present a new method that uses high-precision measurements of eclipsing binary stars, Gaia parallaxes and multi-wavelength photometry to obtain very accurate fundamental effective temperatures. These measurements can be used to establish a set of benchmark stars. Initial results for the F7V+K0IV binary AI Phoenicis are promising: $T_1=6199\pm 22$ K and $T_2=5094\pm 16$ K (Miller, Maxted & Smalley, 2020). We have now applied the method to the newly identified system ASAS J051753-5406.0 (CPD-54 810) and present our preliminary results.