Context :

Aims : We assess the evolutionary status of the intriguing object Walker 90/V590 Mon , which is located about 20 arcminutes northwest of the Cone Nebula near the center of the open cluster NGC 2264 .
This object , according to its most recent optical spectral type determination ( B7 ) , which we confirmed , is at least 3 magnitudes too faint in V for the cluster distance , but it shows the classical signs of a young pre-main sequence object , such as highly variable H \alpha emission , Mg II emission , IR excess , UV continuum , and optical variability .

Methods : We analyzed a collection of archival and original data on Walker 90 , covering 45 years including photometry , imaging , and spectroscopic data ranging from ultraviolet to near-infrared wavelengths .

Results : According to star formation processes , it is expected that , as this object clears its primordial surroundings , it should become optically brighter , show a weakening of its IR excess and present decreasing line emissions .
This behavior is supported by our observations and analysis , but timescales are expected to be longer than the one observed here .
Based on photometric data secured in 2007 , we find Walker 90 at its brightest recorded optical magnitude ( \overline { 12.47 } \pm 0.06 ) .
We document an evolution in spectral type over the past five decades ( from A2/A3 to currently B7 and as early as B4 ) , along with a decrease in the near-infrared K fluxes .
From near-infrared VISIR Â images secured in 2004 , Walker 90 appears as a point source placing an upper limit of < 0.1 \arcsec for its diameter .
Evidence of turbulent inflows is found in rapidly changing inverse P-Cygni profiles in the lower Balmer lines , with a broadening of \pm 400 km/s in H \alpha and a redshifted component in H \beta with a terminal velocity of \sim 600 km/s .
The measured steep UV continuum fluxes ( mimicking a star as early as B4 ) , added to a tentative identification of N V emission , suggest a strong non-photospheric component , typically of fluxes arising from a thermally inhomogeneous accretion disk .
We detect a well defined 2200Ã Â bump , indicative of dense material in the line-of-sight .
We conclude that many observational features are explained if W90 is a flared disk system , surrounded by an inclined optically thick accretion disk .

Conclusions :