  We report the detection of a heavily obscured Active Galactic Nucleus (AGN)
in the luminous infrared galaxy (LIRG) NGC 6286, identified in a 17.5 ks NuSTAR
observation. The source is in an early merging stage, and was targeted as part
of our ongoing NuSTAR campaign observing local luminous and ultra-luminous
infrared galaxies in different merger stages. NGC 6286 is clearly detected
above 10 keV and, by including the quasi-simultaneous Swift/XRT and archival
XMM-Newton and Chandra data, we find that the source is heavily obscured
[$N_{\rm\,H}\simeq (0.95-1.32)\times 10^{24}\rm\,cm^{-2}$], with a column
density consistent with being Compton-thick [CT, $\log (N_{\rm\,H}/\rm
cm^{-2})\geq 24$]. The AGN in NGC 6286 has a low absorption-corrected
luminosity ($L_{2-10\rm\,keV}\sim 3-20\times 10^{41}\rm\,erg\,s^{-1}$) and
contributes $\lesssim$1\% to the energetics of the system. Because of its
low-luminosity, previous observations carried out in the soft X-ray band ($<10$
keV) and in the infrared did not notice the presence of a buried AGN. NGC 6286
has multi-wavelength characteristics typical of objects with the same infrared
luminosity and in the same merger stage, which might imply that there is a
significant population of obscured low-luminosity AGN in LIRGs that can only be
detected by sensitive hard X-ray observations.
