Testing the stability and reliability of starspot modelling

Since the mid 70’s different starspot modelling techniques have been used to describe the observed spot variability on active stars. Spot positions and temperatures are calculated by application of surface integration techniques or solution of analytic equations on observed photometric data.Artificial spotted light curves were generated, by use of the analytic expressions of Budding (1977), to test how the different constraints like the intrinsic scatter of the observed data or the angle of inclination affects the spot solutions. Counteractions between the different parameters like inclination, latitude and spot size were also investigated. The results of re-modelling the generated data were scrutinized statistically. It was found, that (1) 0 . m002− 0 . m005 of photometric accuracy is required to recover geometrical spot parameters within an acceptable error box; (2) even a 0 . m03−0 . m05 error in unspotted brightness substantially affects the recovery of the original spot distribution; (3) especially at low inclination, underor overestimation of inclination by 10◦ leads to an important systematic error in spot latitude and size; (4) when the angle of inclination i < ∼ 20◦ photometric spot modelling is unable to provide satisfactory information on spot location and size.