  We present new Karl G. Jansky Very Large Array observations of the compact (~
0.05"), time-variable radio source projected near the center of the
ultracompact HII region W3(OH). The analysis of our new data as well as of VLA
archival observations confirms the variability of the source on timescales of
years and for a given epoch indicates a spectral index of \alpha = 1.3 +- 0.3
(S_\nu \propto \nu^\alpha). This spectral index and the brightness temperature
of the source (~6,500 K) suggest that we are most probably detecting partially
optically thick free-free radiation. The radio source is probably associated
with the ionizing star of W3(OH), but an interpretation in terms of an ionized
stellar wind fails because the detected flux densities are orders of magnitude
larger than expected. We discuss several scenarios and tentatively propose that
the radio emission could arise in a static ionized atmosphere around a fossil
photoevaporated disk.
