K$_{\rm s} \simeq 13.1$ mag about 0.7$^{\prime \prime}$ west ($\sim 100$ AU at $\sim 140$ pc) of the primary star. A low-resolution spectrum gave evidence that it has a late-M to early-L spectral type. Temperature and luminosity can be used to estimate the mass via theoretical evolutionary models. They are, however, very uncertain at young ages (up to at least $\sim 10$ Myr; Chabrier et al. 2005). Using the Wuchterl & Tscharnuter (2003) model extended to planetary masses and few Myr of age, the GQ Lup companion could be a 1 to 3 M$_{\rm Jup}$ object; whereas for the Tucson group models (Burrows et al. 1997), it is few to $\sim 30$ M$_{\rm Jup}$; and for the Lyon group models (Baraffe et al. 2002), it is few to $\sim 40$ M$_{\rm Jup}$. A comparison with the GAIA-1 model atmospheres indicated low gravity and, hence, a young age and very low mass (N05). Marois et al. (2007) re-analyzed archival HST and Subaru data to study the spectral energy distribution of GQ Lup A and its companion, showing possible evidence for an excess in the L- and R-bands (for the companion), possibly due to a disk and H$\alpha$ emission; a fit of 