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We previously reported the direct detection of a low mass companion at aprojected separation of 55+-2 AU around the B9 type star {\kappa} Andromedae.The properties of the system (mass ratio, separation) make it a benchmark forthe understanding of the formation and evolution of gas giant planets and browndwarfs on wide-orbits. We present new angular differential imaging (ADI) imagesof the Kappa Andromedae system at 2.146 (Ks), 3.776 (L'), 4.052 (NB 4.05) and4.78 {\mu}m (M') obtained with Keck/NIRC2 and LBTI/LMIRCam, as well as moreaccurate near-infrared photometry of the star with the MIMIR instrument. Wederive a more accurate J = 15.86 +- 0.21, H = 14.95 +- 0.13, Ks = 14.32 +- 0.09mag for {\kappa} And b. We redetect the companion in all our high contrastobservations. We confirm previous contrasts obtained at Ks and L' band. Wederive NB 4.05 = 13.0 +- 0.2 and M' = 13.3 +- 0.3 mag and estimateLog10(L/Lsun) = -3.76 +- 0.06. We build the 1-5 microns spectral energydistribution of the companion and compare it to seven PHOENIX-based atmosphericmodels in order to derive Teff = 1900+100-200 K. Models do not set constrainson the surface gravity. ``Hot-start" evolutionary models predict masses of14+25-2 MJup based on the luminosity and temperature estimates, and consideringa conservative age range for the system (30+120-10 Myr). ``warm-start"evolutionary tracks constrain the mass to M >= 11 MJup. Therefore, the mass of{\kappa} Andromedae b mostly falls in the brown-dwarf regime, due to remaininguncertainties in age and mass-luminosity models. According to the formationmodels, disk instability in a primordial disk could account for the positionand a wide range of plausible masses of {\kappa} And b.

Characterization of the gaseous companion {\kappa} Andromedae b: New Keck and LBTI high-contrast observations