X-ray Luminosity Functions of Young Stars in Taurus-Auriga-Perseus

A detailed discussion of the X-ray luminosity functions of pre-main sequence and young main-sequence objects in the Taurus-AurigaPerseus region based on the ROSAT archive is presented. One of the main conclusions is that the XLF of classical and weak-line T Tauri stars (TTS) are different: weak-line TTS are X-ray brighter than classical TTS. Various possible biases related to the sample selection are described and ruled out as a reason for the observed discrepancies. The X-ray emission of the TTS is compared to that of the Pleiades and the Hyades to examine the influence of stellar evolution on the activity level.