  We present a complete low-resolution (R~100) near-infrared spectrum of the
substellar object GY11, member of the rho-Ophiuchi young association. The
object is remarkable because of its low estimated mass and age and because it
is associated with a mid-infrared source, an indication of a surrounding dusty
disk. Based on the comparison of our spectrum with similar spectra of field
M-dwarfs and atmospheric models, we obtain revised estimates of the spectral
type, effective temperature and luminosity of the central object. These
parameters are used to place the object on a Hertzprung-Russell diagram and to
compare with the prediction of pre-main sequence evolutionary models. Our
analysis suggests that the central object has a very low mass, probably below
the deuterium burning limit and in the range 8-12MJupiter, and a young age,
less than 1Myr. The infrared excess is shown to be consistent with the emission
of a flared, irradiated disk similar to those found in more massive brown dwarf
and TTauri systems. This result suggests that substellar objects, even the
so-called isolated planetary mass objects, found in young stellar associations
are produced in a similar fashion as stars, by core contraction and
gravitational collapse.
