LINEAR-POLARIZATION OBSERVATIONS OF T-TAURI STARS .2. A SAMPLE OF OBJECTS FAINTER THAN 13TH MAGNITUDE

We present a northern extension to about 15th mag of previous linear polarization surveys of T Tauri stars and other young stellar objects. These surveys were complete to the 13th mag. Our sample comprises 59 stars; 40 stars are fainter than 13th mag, and are observed for the first time with polarimetry, while the remainder are brighter T.Tauri stars for which we present repeat observations to check for variability. We find that 15 of the newly observed stars display large values of intrinsic polarization, i.e., in excess of is similar to 3%. We show that the statistics of the polarization data for T Tauri stars are compatible with the model of an optically thick circumstellar disk surrounding them. A complete list of all known polarimetrically variable, suspected variable, and nonvariable T Tauri stars known to date is given. We conclude that at least 43% and perhaps all T Tauri stars are polarimetric variables.