| Description |
We propose Herschel dual-band PACS photometry for a unique set of 20 stars that host on-going activity in the terrestrial planet zones and evidence of an outer/colder dust component, to continue the exploration, begun with Spitzer, of their disk structure and composition. The 20 solar- and A-type stars in this sample have combined Spitzer IRS+MIPS (5 to 70 m) SEDs suggesting a two-ring disk architectures that mirror that of the asteroidal-Kuiper belt geometry of our own solar system. However, the extents of the outer zones are unconstrained due to the lack of data beyond 70 m. Also, because the warm belts in our sampleacross the B8 thru K0 stellar spectral rangehave a median dust temperature of 190 K, slightly warmer than that expected at the snow line, we have reason to believe that there is a common grain creation mechanism operating in the inner regions of the star-disk systems, perhaps related to icy planetesimals in a cold outer regions. Herschel provides the observational sensitivity at PACS 100 and 160 m required to successfully constrain the long wavelength emission of the outer/cold disks, and possibly resolve a subset of them. In summary, the PACS observations will: 1) establish the characteristic dust temperature of the outer/cold belts and constrain the minimum mass and position of the debris rings;2) possibly resolve the spatial extend of a subset of systems;3) advance our understanding of dust particle composition by constraining the long wavelength emission;4) facilitate comparison of dust distributions across stellar spectral range;and 5) establish the overall architecture of the circumstellar dust, perhaps pointing to favorable regions where exoplanets may reside.We request 8.0 hours total in PACS AORs using the mini-scan map mode for point-sources, selecting the green (85125 m) and red (125-210 m) lters to constrain the long wavelength emission for all targets. |
