We present the first results of an ongoing campaign using the STIS
spectrograph on-board the Hubble Space Telescope (HST) whose primary
goal is the study of near ultraviolet (UV) spectra of local Type Ia
supernovae (SNe Ia). Using events identified by the Palomar Transient
Factory and subsequently verified by ground-based spectroscopy, we
demonstrate the ability to locate and classify SNe Ia as early as 16
days prior to maximum light. This enables us to trigger HST in a
non-disruptive mode to obtain near UV spectra within a few days of
maximum light for comparison with earlier equivalent ground-based
spectroscopic campaigns conducted at intermediate redshifts, z ~ 0.5. We
analyze the spectra of 12 Type Ia supernovae located in the Hubble flow
with 0.01 < z < 0.08. Although a fraction of our eventual sample,
these data, together with archival data, already provide a substantial
advance over that previously available. Restricting samples to those of
similar phase and stretch, the mean UV spectrum agrees reasonably
closely with that at intermediate redshift, although some differences
are found in the metallic absorption features. A larger sample will
determine whether these differences reflect possible sample biases or
are a genuine evolutionary effect. Significantly, the
wavelength-dependent dispersion, which is larger in the UV, follows
similar trends to that observed at intermediate redshift and is driven,
in part, by differences in the various metallic features. While the
origin of the UV dispersion remains uncertain, our comparison suggests
that it may reflect compositional variations amongst our sample rather
than being predominantly an evolutionary effect.
