$J-K_{\rm s}$ colour of -0.94 approximately translates into a $J-K$ colour of -1.02 [@Stephens.2004; @Leggett.2010].

   ![image](14277fg6a.ps)   ![image](14277fg6b.ps)
  ------------------------ ------------------------
   ![image](14277fg6c.ps)   ![image](14277fg6d.ps)

A second follow-up run at NTT on July 2009, confirmed 2 other ultra-red objects, CFBDSIR221903.07+002417.92 and CFBDSIR221505.06+003053.11 (hereafter CFBDSIR2219 and CFBDSIR2215), with even redder $z'-J$ colours, typical of ultracool brown dwarfs. These objects have redder $z'-J$ than any known T8+ brown dwarf. CFBDSIR2215, however, has only a moderately blue $J-H$ colour, which would be compatible with an earlier (i.e. T5-T7) spectral type, suggesting a peculiar spectrum. The photometric properties of these objects are described in Table \[colours\] and Fig. \[zJJH\].

   Filter        $z'$             $J$              $H$              $K$s
  -------- ---------------- ---------------- ---------------- ----------------
   Mag(1)   $23.60\pm$0.24   19.66$\pm$0.02   20.12$\pm$0.13   20.60$\pm$0.37
   Mag(2)         -          19.72$\pm$0.04   19.96$\pm$0.16   20.13$\pm$0.32

  : (1) $J,~H,~Ks$ CFHT WIRCam Vega photometry and $z'_{AB}$ MegaCam photometry of CFBDSIR1458. (2)$J,~H,~Ks$ NTT SOFI Vega photometry. \[mag\]

         Object            $z'-J$            $J-H$            $J-K$       
  -------------------- --------------- ----------------- ---------------- --
   ULAS0034$~^{1,3}$    3.90$\pm$0.06   -0.28$\pm$0.05    -0.12$\pm$0.06  
    CFBDS0059$~^{2}$    3.86$\pm$0.06   -0.21$\pm$0.06    -0.67$\pm$0.06  
   ULAS1335$~^{1,5}$    4.14$\pm$0.10   -0.35$\pm$0.01    -0.38$\pm$0.03  
   2MASS0939$~^{1,4}$         -         0.18$\pm$0.181    -0.58$\pm$0.10  
    WOLF940B$~^{6}$     3.99$\pm$0.13   -0.61$\pm$0.04    -0.69$\pm$0.05  
      CFBDSIR1458       3.94$\pm$0.24   -0.46$\pm$0.13    -1.02$\pm$0.37  
      CFBDSIR2219       4.45$\pm$0.10   -0.20$\pm$0.085         -         
      CFBDSIR2215       4.30$\pm$0.12   -0.11$\pm$0.08          -         

  : Colours of ultracool brown dwarfs.\[colours\]

References:

$^1$@Leggett.2009, $^2$@Delorme.2008a $^3$@Warren.2007, $^4$@Tinney.2005, $^5$@Burningham.2008, $^6$@Burningham.2009

While CFBDSIR2219 and CFBDSIR2215 are queued 