Extreme Debris Disks and Disk Variability
Abstract
"Extreme debris disks" refers to a class of the planetary debris disks with excesses at 24 microns by at least a factor of four over the photospheric outputs of their stars. Some extreme debris disks are known to have variable emission over timescales of order 1 year and shorter, even a month or less. In general, these systems have strong mineralogical features in their mid-infrared spectra, indicative of very finely divided dust that must be generated continuously to replace that lost by stellar radiation pressure. It is difficult to explain the very rapid variability of these sources and the transient dust lifetimes without invoking condensation of finely divided grains from silica gas. In fact, a sub-class of extreme debris systems shows solid state features in mid-infrared spectra showing the presence of fine silica (not silicate) dust, evidence for condensation from the gas, and perhaps even for the silica gas itself. Such gas is expected to be a product of high-speed collisions between relatively large planetesimals. Where multi-epoch spectra are available, they usually do not show variability in the spectral features despite the dramatic photometric variations, but high signal to noise spectra are needed to probe this question by comparison with the archival Spitzer IRS spectra. In addition, the improved spectral resolution of the new observations will aid in diagnosing the mineralogy of the dust. The goal of our program (ID 1206) is to obtain high signal to noise MIRI spectra of seven selected objects showing signs of extreme collisions that may trace the progress of terrestrial planet building.
- Publication:
-
JWST Proposal. Cycle 1
- Pub Date:
- July 2017
- Bibcode:
- 2017jwst.prop.1206R