Article Summary #8

EVIDENCE FOR DYNAMICAL CHANGES IN A TRANSITIONAL PROTOPLANETARY DISK WITH MID-INFRARED VARIABILITY

J. Muzerolle et al 2009, ApJ, 704, L15
http://www.iop.org/EJ/abstract/1538-4357/704/1/L15/

Planetary disks are circumstellar, highly dusty disk where planets form around young stars (early stage in the stellar system evolution). Planetary formation is a highly complex phenomenon that so far has been difficult to explain and understand, but the physics structure and evolution of the disk where they form can give more insight into this problem and can constrain the timescales related to planet formation.

So far, it has been known that radiation and viscous energy released from the star heat up the dust in the planetary disk. This hot dust emits radiation in the infrared and can give information about the structure of the disk. This paper presents an investigation conducted in the mid-infrared energy range spectroscopy using data from the Spitzer Space Telescope. The thermal emission from the dust is traced with spectral energy distribution (SED) analysis and with these observations they found the locations of the planet-forming regions in the planetary disk.

Currently, there have been important relationships found between he frequency of the disk and the stellar age and mass, though, in previous investigations what was not taken into consideration, and what this paper focuses on, is the dynamics and accreting behavior of the planetary disk. What they found is a large variability in the height of the disk (seen in the SEDs) and they argue two possible explanations for this behavior: 1) the disk mass-accretion varies in time and that can cause changes in the flux irradiate by the disk and in the in situ density of the disk gas (this theory does not fully explain all the observations yet and needs more supporting evidence); 2) the inner disk becomes dynamically perturbed by either a star or planet and the variations in the emitting are of the inner disk causes shadowing in the outer disk. The presence of that companion (star or planet) can also be explained by a gap in the disk observed in the SED shape.

Further research and long-term infrared monitoring can reveal the periodicity in the flux variations from the disk and the inner disk region could be better resolved with long-baseline interferometry.