Metallicity E ects in NLTE Model Atmospheres of Type Ia Supernovae

We have calculated a grid of photospheric phase atmospheres of Type Ia super-novae (SNe Ia) with metallicities from ten times to one thirtieth the solar metallicity in the C+O layer of the deeagration model, W7. We have modeled the spectra using the multipurpose NLTE model-atmosphere and spectrum-synthesis code, PHOENIX. We show models for the epochs 7, 10, 15, 20, and 35 days after explosion. When compared to observed spectra obtained at the approximately corresponding epochs these synthetic spectra t reasonably well. The spectra show variation in the overall level of the UV continuum with lower uxes for models with higher metallicity in the unburned C+O layer. This is consistent with the classical surface cooling and line blocking eeect due to metals in the outer layers of C+O. The UV features also move consistently to the blue with higher metallicity, demonstrating that they are forming at shallower and faster layers in the atmosphere. The potentially most useful eeect is the blueward movement of the Si II feature at 6150 A with increasing C+O layer metallicity. We also demonstrate the more complex eeects of metallicity variations by modifying the 54 Fe content of the incomplete burning zone in W7 at maximum light. We brieey address some shortcomings of the W7 model when compared to observations. Finally, we identify that the split in the Ca H+K feature produced in W7 and observed in some SNe Ia is due to a blending eeect of Ca II and Si II and does not necessarily represent a complex abundance or ionization eeect in Ca II.