  The near-maximum spectra of the Type Ia SN 1999ee are reviewed. Two narrow
absorption features corresponding to the strongest component of the CaII IR
triplet appear in the spectra from 7 days before to 2 days after B-band
maximum, at a high velocity (~22,000 km/s). Before these features emerge, the
CaII IR triplet has an anomalously high velocity, indicating that the narrow
features were still blended with the main, photospheric component.
High-velocity CaII absorption has been observed in other SNe Ia, but usually
detached from the photospheric component. Furthermore, the SiII 6355A line is
observed at a comparably high velocity (~20,000 km/s) 9 and 7 days before B
maximum, but then it suddenly shifts to much lower velocities. Synthetic
spectra are used to reproduce the data under various scenarios. An abundance
enhancement requires an outer region dominated by Si and Ca, the origin of
which is not easy to explain in terms of nuclear burning. A density enhancement
leads to a good reproduction of the spectral evolution if a mass of ~0.10 Msun
is added at velocities between 16,000 and 28,000 km/s, and it may result from a
perturbation, possibly angular, of the explosion. An improved match to the CaII
IR triplet at the earliest epoch can be obtained if the outermost part of this
modified density profile is assumed to be dominated by H (~0.004 Msun above
24,000 km/s). Line broadening is then the result of increased electron
scattering. This H may be the result of interaction between the ejecta and
circumstellar material.
