Analysis of the Early-Time Optical Spectra of SN 2011fe in M101

Abstract : The nearby Type Ia supernova SN 2011fe in M101 (cz=241 km s^-1) provides a unique opportunity to study the early evolution of a "normal" Type Ia supernova, its compositional structure, and its elusive progenitor system. We present 18 high signal-to-noise spectra of SN 2011fe during its first month beginning 1.2 days post-explosion and with an average cadence of 1.8 days. 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 16,000 km s^-1. This supports the notion that incomplete burning, in addition to progenitor scenarios, is a relevant source of spectroscopic diversity among SNe Ia. The observed evolution of the highly Doppler-shifted O I 7774 absorption features detected within five days post-explosion indicate the presence of O I with expansion velocities from 11,500 to 21,000 km s^-1. The fact that some O I is present above C II suggests that SN 2011fe may have had an appreciable amount of unburned oxygen within the outer layers of the ejecta.
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Soumis le : lundi 30 juillet 2012 - 14:11:08
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J.T. Parrent, D. A. Howell, B. Friesen, R. C. Thomas, R. A. Fesen, et al.. Analysis of the Early-Time Optical Spectra of SN 2011fe in M101. Astrophysical Journal Letters, 2012, 752, pp.L26. 〈10.1088/2041-8205/752/2/L26〉. 〈in2p3-00721794〉



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