– 25 – 5.1.3. SED morphologies and fractional disk luminosities In addition to the disk mass, accretion rate, and multiplicity, the SED morphology and fractional disk luminosity of a transition disk can provide important clues on the nature of the object. In this section, we quantify the SED morphologies and fractional disk luminosities of our transition objects in order to compare them to the values of objects with “full disks”. The diversity of SED morphologies seen in transition disks can not be properly captured by the traditional classification scheme of young stellar objects (i.e., the class I through III system), which is based on the slope of the SED between 2 and 25 µ m (Lada 1987). Instead, we quantify the SED “shape” of our targets adopting the two-parameter scheme introduced by Cieza et al. (2007), which is based on the longest wavelength at which the observed flux is dominated by the stellar photosphere, λ$_{turn}$$_{−}$$_{off}$ , and the slope of the IR excess, α$_{excess}$ , computed as dlog( λ F)/dlog( λ ) between λ$_{turn}$$_{−}$$_{off}$ and 24 µ m. The λ$_{turn}$$_{−}$$_{off}$ and α$_{excess}$ values for our entire sample are listed in Table 3. The λ$_{turn}$$_{−}$$_{off}$ and α$_{excess}$ parameters provide useful information on the structure of the disk. In particular, λ$_{turn}$$_{−}$$_{off}$ clearly correlates with the size of the inner hole as it depends on the temperature of the dust closest to the star. Wien’s displacement law implies that Spitzer ’s 3.6, 4.5, 5.8, 8.0, and 24 µ m bands best probe dust temperatures of roughly 780K, 620K, 480K, and 350K, and 120K, respectively. For stars of solar luminosity, these temperatures correspond to circumstellar distances of ≲ 1 AU for the IRAC bands and ∼ 10 AU for the 24 µ m MIPS band. Similarly, α$_{excess}$ correlates well with the sharpness of the hole: a sharp inner hole, such as that of CoKu Tau/4, is characterized by a large and positive α$_{excess}$ value, while a continuous disk that has undergone significant grain growth and dust settling is characterized by a large negative α$_{excess}$ value (Dullemond & Dominik, 2004). However, the λ$_{turn}$$_{−}$$_{off}$ and α$_{excess}$ parameters should be interpreted with caution.