Dependence of rms residual on rotation period. Black points represent individual models, and the blue curve is a running mean of residuals over 31 points centered at the middle period. Red squares mark known tumblers (T or T+ tag in the Lightcurve Database of Warner et al. (2009)), and yellow triangles mark asteroids that are known to be in the principal-axis rotation state, i.e., not tumbling (T−).