Analysis of the early-time optical spectra of SN 2011fe in M101

J. T. Parrent, D. A. Howell, B. Friesen, R. C. Thomas, R. A. Fesen, D. Milisavljevic, F. B. Bianco, B. Dilday, P. Nugent, E. Baron, I. Arcavi, S. Ben-Ami, D. Bersier, L. Bildsten, J. Bloom, Y. Cao, S. B. Cenko, A. V. Filippenko, A. Gal-Yam, M. M. KasliwalN. Konidaris, S. R. Kulkarni, N. M. Law, D. Levitan, K. Maguire, P. A. Mazzali, E. O. Ofek, Y. Pan, D. Polishook, D. Poznanski, R. M. Quimby, J. M. Silverman, A. Sternberg, M. Sullivan, E. S. Walker, Dong Xu, C. Buton, R. Pereira

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish
Article numberL26
JournalAstrophysical Journal Letters
Issue number2
StatePublished - 20 Jun 2012


  • supernovae: general
  • supernovae: individual (SN 2011fe)


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