We present the first characterization of the excess continuum emission of
accreting T Tauri stars between optical and near-infrared wavelengths. With
nearly simultaneous spectra from 0.48 to 2.4 microns acquired with HIRES and
NIRSPEC on Keck and SpeX on the IRTF, we find significant excess continuum
emission throughout this region, including the I, Y, and J bands, which are
usually thought to diagnose primarily photospheric emission. The IYJ excess
correlates with the excess in the V band, attributed to accretion shocks in the
photosphere, and the excess in the K band, attributed to dust in the inner disk
near the dust sublimation radius, but it is too large to be an extension of the
excess from these sources. The spectrum of the excess emission is broad and
featureless, suggestive of blackbody radiation with a temperature between 2200
and 5000 K. The luminosity of the IYJ excess is comparable to the accretion
luminosity inferred from modeling the blue and ultraviolet excess emission and
may require reassessment of disk accretion rates. The source of the IYJ excess
is unclear. In stars of low accretion rate, the size of the emitting region is
consistent with cooler material surrounding small hot accretion spots in the
photosphere. However, for stars with high accretion rates, the projected area
is comparable to or exceeds that of the stellar surface. We suggest that at
least some of the IYJ excess emission arises in the dust-free gas inside the
dust sublimation radius in the disk.Comment: Accepted to ApJ, 31 pages, 21 figure
