期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 477, 期 3, 页码 3567-3582出版社
OXFORD UNIV PRESS
DOI: 10.1093/mnras/sty820
关键词
line: profiles; techniques: spectroscopic; supernovae: general
资金
- UK Science and Technology Facilities Council (STFC) through an Ernest Rutherford Fellowship [ST/M005348/1]
- STFC [ST/P000312/1]
- Alexander von Humboldt Fellowship
- US National Science Foundation (NSF) [AST-1311862]
- EU/FP7-ERC [615929]
- NSF [AST-1313484]
- Aerospace Corporations Technical Investment Program
- Max Planck Institute for Astronomy, Heidelberg
- Max Planck Institute for Extraterrestrial Physics, Garching
- Johns Hopkins University, Durham University
- University of Edinburgh
- Queen's University Belfast
- Harvard-Smithsonian Center for Astrophysics
- Las Cumbres Observatory Global Telescope Network Incorporated
- National Central University of Taiwan
- Space Telescope Science Institute
- National Aeronautics and Space Administration through the Planetary Science Division of the NASA Science Mission Directorate [NNX08AR22G]
- National Science Foundation [AST-1238877]
- University of Maryland, Eotvos Lorand University (ELTE)
- Los Alamos National Laboratory
- Gordon and Betty Moore Foundation
- Institute for Astronomy
- University of Hawaii
- Pan-STARRS Project Office
- Max-Planck Society and its participating institutes
- European Organization for Astronomical Research in the Southern Hemisphere, Chile , PESSTO [091.D-0764(A), 092.D-0632(A), 096.D-0627(A), 188.D-3003]
- National Aeronautics and Space Administration
- STFC [ST/M005348/1, ST/P000312/1] Funding Source: UKRI
The late-time spectra of Type Ia supernovae (SNe Ia) are powerful probes of the underlying physics of their explosions. We investigate the late-time optical and near-infrared spectra of seven SNe Ia obtained at the VLT with XShooter at >200 d after explosion. At these epochs, the inner Fe-rich ejecta can be studied. We use a line-fitting analysis to determine the relative line fluxes, velocity shifts, and line widths of prominent features contributing to the spectra ([Fe II], [Ni II], and [Co III]). By focusing on [Fe II] and [Ni II] emission lines in the similar to 7000-7500 angstrom region of the spectrum, we find that the ratio of stable [Ni II] to mainly radioactively produced [Fe II] for most SNe Ia in the sample is consistent with Chandrasekhar-mass delayed-detonation explosion models, as well as sub-Chandrasekhar mass explosions that have metallicity values above solar. The mean measured Ni/Fe abundance of our sample is consistent with the solar value. The more highly ionized [Co III] emission lines are found to be more centrally located in the ejecta and have broader lines than the [Fe II] and [Ni II] features. Our analysis also strengthens previous results that SNe Ia with higher Si II velocities at maximum light preferentially display blueshifted [Fe II] 7155 angstrom lines at late times. Our combined results lead us to speculate that the majority of normal SN Ia explosions produce ejecta distributions that deviate significantly from spherical symmetry.
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