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Title: A Rapid Ionization Change in the Nebular-phase Spectra of the Type Ia SN 2011fe
Abstract

We present three new spectra of the nearby Type Ia supernova (SN Ia) 2011fe covering ≈480–850 days after maximum light and show that the ejecta undergoes a rapid ionization shift at ∼500 days after explosion. The prominent Feiiiemission lines at ≈4600 Å are replaced with Fei+Feiiblends at ∼4400 Å and ∼5400 Å. The ≈7300 Å feature, which is produced by [Feii]+[Niii] at ≲400 days after explosion, is replaced by broad (≈±15,000 km s−1) symmetric [Caii] emission. Models predict this ionization transition occurring ∼100 days later than what is observed, which we attribute to clumping in the ejecta. Finally, we use the nebular-phase spectra to test several proposed progenitor scenarios for SN 2011fe. Nondetections of H and He exclude nearby nondegenerate companions, [Oi] nondetections disfavor the violent merger of two white dwarfs, and the symmetric emission-line profiles favor a symmetric explosion.

Authors:
; ; ; ; ;
Award ID(s):
1814440
Publication Date:
NSF-PAR ID:
10363205
Journal Name:
The Astrophysical Journal Letters
Volume:
926
Issue:
2
Page Range or eLocation-ID:
Article No. L25
ISSN:
2041-8205
Publisher:
DOI PREFIX: 10.3847
Sponsoring Org:
National Science Foundation
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