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tokens: that ongoing accretion is occurring at such a slow rate that it is not detectable and that we caught H α in emission when the accretion was barely high enough to detect. Despite the evidence for some gas in the disk and its young age, the disk fractional luminosity and low dust mass of T 43 is consistent with what is seen in debris disks. We conclude that T 54 has ended its primordial disk lifetime and is crossing over the bridge to the debris disks stage. The fact that this is a binary system hastens its evolution, allowing us a rare glimpse of this bridge in a young star-forming region. Future observations of this object will help us understand this short-lived stage. Appendix T 54 has a nearby FIR source that contaminates the observed FIR emission (left, Figure 9 ; Matrà et al. 2012 ). Here we show that this unidentified FIR source should have no significant contribution to most of the data that we study in this paper. The unidentified FIR source is 6′′ away from T 54. Assuming it is in Cha I (at 160 pc), it is located 1040 au away from T 54 at a position angle of 196°. To the best of our knowledge, this FIR source does not overlap with previously reported objects. Figure 9. Left: PACS 70 μ m image from the HSA archive with T 54 and a nearby 2MASS source labeled with red triangles (top and lower, respectively). The FIR source identified by Matrà et al. ( 2012 ) is denoted with a black ellipse. Center: Spitzer IRS spectral footprint overlaid on the PACS 70 μ m image. We show the short-low (yellow) and long-low (black) slits as well as the two nods of the short-high observations (red). Right: Herschel PACS spectral footprint (red boxes) corresponding to the [O i ] observations discussed in Section 4.1.4 overlaid on the PACS 70 μ m image. Note that T 54 is in the central spaxel, which was used to extract the spectrum, and the unidentified FIR source is not covered by the central spaxel. Matrà et al. ( 2012 ) find that the unidentified FIR source is not detected in JHK -band photometry, IRAC photometry, or MIPS data taken at 24 μ m. However, it is detected in PACS 70 and 100 μ m data as well as in SPIRE photometry taken at 160, 250, and 350 μ m. The flux of this unidentified FIR source is comparable to or greater than the flux of T 54 at 100 μ m and beyond (Matrà et al. 2012 ). Therefore we show in Figure 8 the fluxes reported by Matrà et al. ( 2012 ) as upper limits since these data include emission from both the T 54 system and the nearby unidentified FIR source. It is unlikely that the unidentified FIR source is contributing to the Spitzer IRS spectra of T 54. As reported by Matrà et al. ( 2012 ), the unidentified FIR source is not detected in NIR, MIR IRAC, or MIPS images. To explore this further, we overlaid the IRS slit positions on a PACS 70 μ m image of T 54 (center panel, Figure 9 ). Low- and high-resolution IRS spectral observations of T 54 are available in CASSIS. In the low-resolution observations (2005 April 24 10:57:08), the