  Over a timescale of a few years, an observed change in the optically thick
radio continuum flux can indicate whether an unresolved H II region around a
newly formed massive star is changing in size. In this Letter we report on a
study of archival VLA observations of the hypercompact H II region G24.78+0.08
A1 that shows a decrease of ~ 45 % in the 6-cm flux over a five year period.
Such a decrease indicates a contraction of ~ 25 % in the ionized radius and
could be caused by an increase in the ionized gas density if the size of the H
II region is determined by a balance between photoionization and recombination.
This finding is not compatible with continuous expansion of the H II region
after the end of accretion onto the ionizing star, but is consistent with the
hypothesis of gravitational trapping and ionized accretion flows if the
mass-accretion rate is not steady.
