X-ray emission from young stars in Taurus-Auriga-Perseus: Luminosity functions and the rotation activity age relation

We report on a systematic search for X-ray emission from pre-main sequence and young main sequence stars in the Taurus-Auriga-Perseus region. Our stel lar sample consists of all T Tauri stars from the Taurus-Auriga region, and all late-type stars from the Pleiades and Hyades clusters which have been observed by the ROSAT PSPC in pointed observations. We present the X-ray pa rameters for all observed stars in tables. Next to the basic results of the data analysis (such as count rates, exposure time, and off-axis angle) we give X-ray luminosities and hardness ratios for all detected stars. Upper l imits are given for non-detections. Detection rates for different spectral types are compiled. We use these results to study the connection between co ronal X-ray activity and stellar parameters for different subgroups of our sample. In particular we compile X-ray luminosity functions (XLF), and disc uss the relations between X-ray emission and spectral type, age, and rotati on, which have been disputed extensively in the past. Here, we study these questions with the largest sample so far. The XLF for classical and weak-li ne T Tauri stars are different, with weak-lines being the stronger X-ray em itters. Proceeding towards the main-sequence (Pleiades, Hyades) the X-ray l uminosity declines for all spectral types examined (G, K, and M stars). Wit hin an age group L-x decreases towards later spectral types, while L-x=L-bo l remains constant or even increases, reflecting the opposed influence of s tellar radius, i.e. emitting area, and convection zone depth. For a given s pectral type the fastest rotators show the highest X-ray luminosity. Rotati on rate and X-ray emission are clearly correlated for all groups of stars w ith power law indices for log (L-x=L-bol) versus log P-rot of similar to -0 .7 to 1.5. The study of XLF for binary stars shows that the known unresolve d secondaries likely contribute a significant amount to the X-ray emission.