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The study of hyper-compact (HC) or ultra-compact (UC) HII regions isfundamental to understanding the process of massive (> 8 M_sun) star formation.We employed Atacama Large Millimeter/submillimeter Array (ALMA) 1.4 mm Cycle 6observations to investigate at high angular resolution (~0.050", correspondingto 330 au) the HC HII region inside molecular core A1 of the high-massstar-forming cluster G24.78+0.08. We used the H30alpha emission and differentmolecular lines of CH3CN and 13CH3CN to study the kinematics of the ionized andmolecular gas, respectively. At the center of the HC HII region, at radii <~500au, we observe two mutually perpendicular velocity gradients, which aredirected along the axes at PA = 39 deg and PA = 133 deg, respectively. Thevelocity gradient directed along the axis at PA = 39 deg has an amplitude of 22km/s mpc^(-1), which is much larger than the other's, 3 km/s mpc^(-1). Weinterpret these velocity gradients as rotation around, and expansion along, theaxis at PA = 39 deg. We propose a scenario where the H30alpha line traces theionized heart of a disk-jet system that drives the formation of the massivestar (~20 M_sun) responsible for the HC HII region. Such a scenario is alsosupported by the position-velocity plots of the CH3CN and 13CH3CN lines alongthe axis at PA = 133 deg, which are consistent with Keplerian rotation around a20 M_sun star. Toward the HC HII region in G24.78+0.08, the coexistence of massinfall (at radii of ~5000 au), an outer molecular disk (from <~4000 au to >~500au), and an inner ionized disk (<~500 au) indicates that the massive ionizingstar is still actively accreting from its parental molecular core. To ourknowledge, this is the first example of a molecular disk around a high-massforming star that, while becoming internally ionized after the onset of the HIIregion, continues to accrete mass onto the ionizing star.

The ionized heart of a molecular disk. ALMA observations of the hyper-compact HII region G24.78+0.08 A1