- Parrent, JT;
- Howell, DA;
- Friesen, B;
- Thomas, RC;
- Fesen, RA;
- Milisavljevic, D;
- Bianco, FB;
- Dilday, B;
- Nugent, P;
- Baron, E;
- Arcavi, I;
- Ben-Ami, S;
- Bersier, D;
- Bildsten, L;
- Bloom, J;
- Cao, Y;
- Cenko, SB;
- Filippenko, AV;
- Gal-Yam, A;
- Kasliwal, MM;
- Konidaris, N;
- Kulkarni, SR;
- Law, NM;
- Levitan, D;
- Maguire, K;
- Mazzali, PA;
- Ofek, EO;
- Pan, Y;
- Polishook, D;
- Poznanski, D;
- Quimby, RM;
- Silverman, JM;
- Sternberg, A;
- Sullivan, M;
- Walker, ES;
- Xu, Dong;
- Buton, C;
- Pereira, R
The nearby Type Ia supernova (SNIa) SN2011fe in M101 (cz = 241kms -1) provides a unique opportunity to study the early evolution of a "normal" SNIa, its compositional structure, and its elusive progenitor system. We present 18 high signal-to-noise spectra of SN2011fe during its first month beginning 1.2days post-explosion and with an average cadence of 1.8days. This gives a clear picture of how various line-forming species are distributed within the outer layers of the ejecta, including that of unburned material (C+O). We follow the evolution of C II absorption features until they diminish near maximum light, showing overlapping regions of burned and unburned material between ejection velocities of 10,000 and 16,000kms-1. This supports the notion that incomplete burning, in addition to progenitor scenarios, is a relevant source of spectroscopic diversity among SNeIa. The observed evolution of the highly Doppler-shifted O I λ7774 absorption features detected within 5days post-explosion indicates the presence of O I with expansion velocities from 11,500 to 21,000kms-1. The fact that some O I is present above C II suggests that SN2011fe may have had an appreciable amount of unburned oxygen within the outer layers of the ejecta. © 2012. The American Astronomical Society. All rights reserved..