  We present time series spectrophotometric observations of GQ Lupi, a typical
representative of the YY Ori subgroup of T Tauri stars that show conspicuous
inverse PCygni profiles. The data set consists of 32 exposures taken over 5 and
8 consecutive nights of May and July 1998, respectively, and covers the
spectral range of 3100 \AA~ $< \lambda < 5100 $ \AA. The region redward and
next to the Balmer jump varies significantly on a night-to-night basis and the
amplitude of such variability decreases sharply at $\lambda >$ 4600 \AA. The
Balmer continuum slope indicates that the spectral energy distribution is
governed by a gas of temperature greater than that of the stellar photosphere.
We find an anticorrelation between the veiling and the observed Balmer jump.
The time series of the redward absorption component behaves similarly to the
veiling time series. We model the emitting region by a gas of uniform
temperature and density. The models indicate that the gas densities and the
respective temperatures are strongly anticorrelated. In addition, the model
time series show that the increase in the gas density is mirrored by an
increase of the projected emitting area (filling factor). Large/small gas
densities and filling factors are characterized by high/low observed veiling.
As the accretion rate fades from night-to-night, the observed veiling
decreases, as does the gas density and the total projected emitting area.
