Possible detection of a magnetic field in T Tauri

Medium-resolution (R' 15 000) circular spectropolarimetry of T Tauri is presented. The star was observed twice: on November 11, 1996 and January 22, 2002. Weak circular polarization was found in photospheric absorption lines, indicating a mean surface longitudinal magnetic field Bk of 160 40 G and 140 50 G at the epoch of the first and second observations respectively. While these values are near the detection limit of our apparatus, we belive that they are real. One can conclude from our data that Bk of T Tau does not significantly exceed 200 G, which is much less than surface magnetic field strength of the star (>2.3 kG) found by Guenther et al. (1999) and Johns-Krull et al. (2000). We discuss possible reasons for this dierence.