1. A study of Si <scp>ii</scp> and S <scp>ii</scp> features in spectra of Type Ia supernovae
- Author
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Xiaofeng Wang, Keiichi Maeda, Xulin Zhao, and Hanna Sai
- Subjects
High Energy Astrophysical Phenomena (astro-ph.HE) ,Physics ,010308 nuclear & particles physics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics ,Type (model theory) ,Lambda ,01 natural sciences ,Spectral line ,Supernova ,Space and Planetary Science ,0103 physical sciences ,Saturation (graph theory) ,Absorption (logic) ,Astrophysics - High Energy Astrophysical Phenomena ,10. No inequality ,010303 astronomy & astrophysics ,Energy (signal processing) ,Line (formation) - Abstract
We studied the spectral features of Si II $\lambda\lambda$4130, 5972, 6355 and S II W-trough for a large sample of Type Ia supernovae (SNe Ia). We find that in NV (Normal-Velocity) subclass of SNe Ia, these features tend to reach a maximum line strength near maximum light, except for Si II $\lambda$5972. Spectral features with higher excitation energy, such as S II W-trough, are relatively weak and have relatively low velocity. SNe Ia with larger $\Delta$m$_{15}$($B$) tend to have lower velocities especially at phases after maximum light. NV SNe show a trend of increasing line strength with increasing $\Delta$m$_{15}$($B$), while 91T/99aa-like SNe show an opposite trend. Near maximum light, the absorption depth of Si II $\lambda$5972 shows the strongest correlation with $\Delta$m$_{15}$($B$), while at early times the sum of the depths of Si II $\lambda\lambda$4130 and 5972 shows the strongest correlation with $\Delta$m$_{15}$($B$). The overall correlation between velocity and line strength is positive, but within NV SNe the correlation is negative or unrelated. In normal SNe Ia, the velocity-difference and depth-ratio of a longer-wavelength feature to a shorter-wavelength feature tend to increase with increasing $\Delta$m$_{15}$($B$). These results are mostly well explained with atomic physics, but some puzzles remain, possibly related to the effects of the saturation, line competition or other factors., Comment: 14 pages, 13 figures. Accepted for publication in MNRAS
- Published
- 2020