We have rereduced Spitzer IRS spectra and reanalyzed the SED ’ s of three nearby debris disks : \lambda Boo , HD 139664 , and HR 8799 .
We find that that the thermal emission from these objects is well modeled using two single temperature black body components .
For HR 8799 – with no silicate emission features despite a relatively hot inner dust component ( T _ { gr } = 150 K ) – we infer the presence of an asteroid belt interior to and a Kuiper Belt exterior to the recently discovered orbiting planets .
For HD 139664 , which has been imaged in scattered light , we infer the presence of strongly forward scattering grains , consistent with icy or porous grains , if the cold , outer disk component generates both the observed scattered light and thermal emission .
Finally , careful analysis of the \lambda Boo SED suggests that this system possesses a central clearing , indicating that selective accretion of solids onto the central star does not occur from a dusty disk .