X-ray Luminosity Functions of Young Stars in Taurus-Auriga-Perseus
  X-ray luminosity functions (XLF) are frequently used to assess the properties of the X-ray emission from a given sample of stars, and particularly important for a comparison of different groups of stars. I present the results from a detailed analysis of the XLF of pre-main sequence T Tauri Stars in Taurus-Auriga and young main-sequence objects (represented by the Pleiades and Hyades cluster). The study is based on the ROSAT public archive. Various possible biases related to the sample selection are described, and their influence on the luminosity distributions is discussed. 
B. Stelzer