– 34 – 5.2.5. Disk Classification Based on the discussion above, we divide our transition disk sample into the following “disk types”: outer disk onto itself. As a result, in the presence of a Jupiter mass planet, the accretion onto the star is expected to be reduced by a factor of 4 to 10 with respect to the accretion across the outer disk (Lubow & D $^{′}$Angelo, 2006). Four of the accreting objects in our sample, targets # 11, 21, 31, and 32 have α$_{excess}$ > 0, suggesting the presence of a sharp inner hole, and are thus excellent candidates for ongoing giant planet formation. Source #32 is a particularly good candidate to be currently forming a massive giant planet, as it has a high disk mass ( ∼ 11 M$_{JUP}$ ) and small accretion rate (10 − 9 . 8 M$_{⊙}$yr − $^{1}$). Sources #11, 21, and 31 (M$_{D}$ < 1.5 M$_{JUP}$ ; M$_{acc}$ ∼ 10 − 9 . $^{3}$-10 − 7 . 3 M$_{⊙}$yr − $^{1}$), could have formed a massive giant planet in the recent past, as in their case most of the disk mass has already been depleted. Since target #21 has been observed with the lunar occultation technique, an equal-mass binary system can be ruled out for this system down to ∼ 1 AU (Simon et al. 1995). Also, it has been proposed that companions with masses of the order of 10 M$_{JUP}$ completely isolate the inner disk from the outer disk and halt the accretion onto the star (Lubow et al. 1999). If that is the case, accretion itself could be evidence against the presence of a close (sub)stellar companion. That said, because a few accreting close binary systems are already known, such as DQ Tau (Carr et al. 2001) and CS Cha (Espaillat et al. 2007), it is clear that accretion does not rule out completely the presence of tight stellar companions. In addition to the mass of the companion, the eccentricity of the orbit, the viscosity and scale height of the disk are also important factors in determining whether or not gap-crossing streams can exist and allow the accretion onto the star to continue (Artymowicz &Lubow 1996).