| Description |
Some pre-main sequence stars exhibit peculiar wavelength-dependence of their mid-infrared spectral variability. This finding led to the proposal of avertically extended obscuring structure in the inner part of the system that casts time-variable shadow on the outer disk. It is an extra component of T Tauri disks not considered in most disk models so far. In our previous optical-to-mid-infrared survey we could directly detect the thermal emission of this obscuring dust cloud. In order to initiate the physical characterization of the shadowing material, we propose a 70/160 um 4-epoch monitoring survey of eight young stars in the Chamaeleon I star forming region with Herschel. For half of this sample our earlier measurements already hint for the presence of a shadowing structure. Simultaneously with the Herschel observations we will also arrange optical-to-mid-infrared observations from the ground. We will perform a correlation analysis between the variability patterns observed at different wavelengths, in order to understand the origin of the obscuring structure. Correlation between optical and far-infrared light curves would favor an orbiting warp or long-lived dust cloud in the inner disk, while anticorrelation is interpreted as a signature of a temporary dust cloud lifted above the disk plane. In both scenarios the probable driving force behind the origin and the temporal rearrangement of this structure is time-variable accretion. Through detailed modeling of the spectral energy distributions and of the wavelength-dependence of the variability, basic physical parameters of the obscuring structure will be derived. Together with the timescale on which its structure can change, these are important entries to learn what kind of dynamical processes occur in the inner disks of low-mass pre-main sequence stars. For this project we request 7.8 h of Herschel observing time. |
