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

  • Author(s): 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, D
  • Buton, C
  • Pereira, R
  • et al.
Abstract

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..

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