  We present the identification of the companion star to the intermediate mass
binary pulsar J1439-5501 obtained by means of ground-based deep images in the
B, V and I bands, acquired with FORS2 mounted at the ESO-VLT. The companion is
a massive white dwarf (WD) with B=23.57+-0.02, V=23.21+-0.01 and I=22.96+-0.01,
located at only ~0.05" from the pulsar radio position. Comparing the WD
location in the (B, B-V) and (V, V-I) Color-Magnitude diagrams with theoretical
cooling sequences we derived a range of plausible combinations of companion
masses (1<~Mcom<~1.3 Msun), distances (d<~1200 pc), radii (<~7.8 10^3 Rsun) and
temperatures (T=31350^{+21500}_{-7400}). From the PSR mass function and the
estimated mass range we also constrained the inclination angle i >~ 55 degrees
and the pulsar mass (Mpsr <~2.2 Msun). The comparison between the WD cooling
age and the spin down age suggests that the latter is overestimated by a factor
of about ten.
