IRAS observations of T Tauri and post-T Tauri stars

Fifty-four T Tauri and eight post-T Tauri stars have been checked for coincidences with the IRAS far-infared sources (at 12, 25, 60, and 100 μm). In that number, 35 single T Tauri stars and one post-T Tauri star have been identified with unconfused sources. Ten additional T Tauri stars in close visual pairs coincide with five confused sources. It is significant that only one post-T Tauri star (FK Ser) has been identified as a far-infrared source and that TW Hya - the only T Tauri star located far from any dark cloud complex - has very typical properties of its far-infrared spectrum. The IRAS data for 36 unconfused sources have been compared with the visual and near-infrared data. A hypothesis that the far-infrared radiation comes from dusty accretion disks of large optical depth has been tested and found plausible (but not necessarily unique). Some T Tauri stars (most notably DG Tau) have large far-infrared excesses which closely resemble that of T Tauri, where it is known to be caused by a cold infrared companion.