We present J –band imaging and H + K –band low-resolution spectroscopy of the 2MASS1207-3932AB system , obtained with the VLT NIR-AO instrument ( NACO ) .
Our J -band astrometry is consistent with AB being a co-moving system , in agreement with the recent results of Chauvin et al .
( 2005a ) .
For the putative planetary mass secondary , we find J = 20.0 \pm 0.2 mag .
The shapes of the HK spectra for both components imply low gravity , as expected for this young ( 5–10 Myr-old ) system , as well as a dusty atmosphere for the secondary .
Comparisons to the latest synthetic spectra yield T _ { eff - A } \approx 2550 \pm 150K , and T _ { eff - B } \approx 1600 \pm 100K .
These temperatures are consistent with the late-M and mid-to-late L spectral types derived earlier for 2M1207A and B respectively .
For these T _ { e f f } , and an age of 5–10 Myrs , the latest theoretical evolutionary tracks imply M _ { A } \approx 24 \pm 6 M _ { Jup } and M _ { B } \approx 8 \pm 2 M _ { Jup } .
Independent comparisons of the theoretical tracks to the observed colors , spanning \sim I to L ^ { \prime } ( including recent HST photometry ) , also yield the same mass and temperature estimates .
Our mass for the primary agrees with other recent analyses ; however , our secondary mass , while still in the planetary regime , is 2–3 times larger than claimed previously .
The roots of this discrepancy can be traced directly to the luminosities : while the absolute photometry and { M } _ { \it bol } of the primary are in excellent agreement with theoretical predictions ( especially with the recently derived d = 53 \pm 6 pc for the system ) , the secondary appears \sim 2.5 \pm 0.5 mag fainter than expected in all photometric bands from I to L ^ { \prime } as well as in { M } _ { \it bol } .
This anomalous under-luminosity accounts for the much lower secondary mass ( and temperature ) derived in earlier studies .
We argue that this effect is highly unlikely to result from : ( i ) a large overestimation of our secondary T _ { e f f } ; ( ii ) serious overestimation of luminosities by the theoretical evolutionary models ; ( iii ) very large distance/age variations between the two components ; or ( iv ) faintness in the secondary due to formation via core-accretion .
These conclusions are bolstered by the absence of any luminosity problems with the primary in our analysis .
Similarly , we find no luminosity discrepancies in the recently discovered sub-stellar companion AB Pic B , which is also young ( age \sim 30 Myr ) and comparable in spectral classification ( \sim L-type ) and temperature ( \sim 1700K ) to 2M1207B .
We therefore suggest grey extinction in 2M1207B , due to occlusion by an edge-on circum-secondary disk .
This scenario is consistent with the observed properties of edge-on disks around T Tauri stars , and with the known presence of a high-inclination evolved disk around the primary .
Finally , the system ’ s implied mass ratio of \sim 0.3 suggests a binary-like formation scenario .