2006ApJ...645..659O

Photometric and spectroscopic techniques have proven to be effective ways to measure the properties of dark, cool starspots on magnetically active stars. Recently, a technique was introduced using atomic line depth ratios (LDRs) to measure starspot properties. Carefully reproducing this technique using a new set of spectroscopic observations of active stars, we find that the LDR technique encounters difficulties, specifically by overestimating spot temperatures (because the atomic lines blend with titanium oxide absorption in cooler spots) and by not tightly constraining the filling factor of spots. While the use of LDRs for active star studies has great promise, we believe that these concerns need to be addressed before the technique is more widely applied.