2004BaltA..13..543G

Circumstellar disks are by-products of the formation of low-mass stars. When young stars become optically visible for the first time two distinct classes of objects are seen: classical and weak-line T Tauri stars. Disks are known to exist around classical T Tauri stars (CTTS). In contrast, weak-line T Tauri stars, WTTS (with much weaker Hα emission) are not expected to have any circumstellar material. The connection between the two classes of young stars is not clear although it has been speculated that in some cases at least CTTS may lose their disks with time and become WTTS, before reaching the zero-age main sequence. Disks around pre-main-sequence stars can be detected by infrared excesses. We have analyzed ISO photometric data of a number of WTTS belonging to different molecular clouds, studied their spectral energy distributions and estimated their ages and masses. In a large number of WTTS we did detect infrared excesses although in some cases this may be due to the presence of embedded nearby companions. Here we examine the evidence of circumstellar material around WTTS.