Program: GS-2011B-Q-15

We have discovered a major obstacle in the use of Type Ia supernovae (SNe Ia) as standard candles: SNe Ia in high and low-mass galaxies correct to different absolute magnitudes. The progenitors matter. Yet we are ignorant of them: everything we know about SNe Ia is from the ashes -- material synthesized in the exploson. For the first time we have studied the fuel, finding, surprisingly, that not all SNe Ia burn completely -- in ~30% of cases, we see carbon from the progenitor. But does this correspond to differences in progenitor scenarios? Does it correlate with SN Ia luminosity or environment? Does metallicity drive environmental differences? Now we have redesigned our search strategy with a two day cadence, and our Gemini strategy to probe SN Ia progenitors on three fronts. With this proposal we will: (1) build the first significant sample of early-time SN Ia spectra with signs of progenitor material, (2) trigger and obtain concurrent ground-based spectra for our Cycle 18 HST STIS ToO program probing progenitor metallcity, and (3) trigger our Keck program looking for circumstellar material in high resolution spectra, which has recently tied a SN Ia to a likely recurrent nova progenitor.