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We present new Karl G. Jansky Very Large Array observations of the compact (~0.05"), time-variable radio source projected near the center of theultracompact HII region W3(OH). The analysis of our new data as well as of VLAarchival observations confirms the variability of the source on timescales ofyears 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 temperatureof the source (~6,500 K) suggest that we are most probably detecting partiallyoptically thick free-free radiation. The radio source is probably associatedwith the ionizing star of W3(OH), but an interpretation in terms of an ionizedstellar wind fails because the detected flux densities are orders of magnitudelarger than expected. We discuss several scenarios and tentatively propose thatthe radio emission could arise in a static ionized atmosphere around a fossilphotoevaporated disk.

The compact, time-variable radio source projected inside W3(OH): Evidence for a Photoevaporated Disk?