The following document lists the file abstract/GSTRINGF_EXORS.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
EXORs, named after the prototype EX Lup, are a very small subclass of classical T Tauri stars (CTTSs) which experience rather major optical outbursts. Outbursts of the EXORs are intermediate between the long lived and more energetic FU Ori type outbursts (FUORs) and the more modest accretion variability of the CTTSs. EXORs undergo large amplitude outbursts as a direct result of enhanced mass accretion from their circumstellar disk. The accretional energy liberated results in a brightening of 3--5 magnitudes in the UV and optical. Direct accretion to the stellar surface can be via a boundary layer or magnetic coupling between the disk and star. The outbursts play a major role in modifying the circumstellar environment, and initiate the formation of winds, jets, and H-H objects, and dispersal of the disk. The large physical changes in the circumstellar environment during such outbursts likely influence the formation and evolution of giant planets and brown dwarfs. EXOR, and the related FUOR, outbursts frequently occur over the disk-accretion lifetime of young stellar objects. However, the characteristics of the EXORs are poorly understood due to the paucity of observational data during both quiescence and in outburst; the PI has ongoing ground-based programs in the optical and near-IR to rectify this. The (variable?) near-IR colors of the EXORs indicate a range of properties, some being optically thin while others are massive and optically thick. Exactly how the disk replenishes itself between outbursts and the underlying mechanism that triggers the outbursts remains a mystery. We propose to obtain the necessary ISO data that will (1) determine the spectral energy distribution of the extended disk, (2) deduce the temperature distribution of the disk and it's composition, (3) determine how rapidly the disk is being replenished and how the temperature structure and composition respond to the infall of matter onto the disk, and (4) gain insight into the trigger mechanism of the outburst and how this affects the outer disk.