Origin of broad He II 4686Å emission in early spectra of type IIP supernovae
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arXiv
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| Format: | Preprint |
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2024
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| _version_ | 1866910347232804864 |
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| author | Chugai, Nikolai Utrobin, Victor |
| author_facet | Chugai, Nikolai Utrobin, Victor |
| contents | We propose a model for the origin of the broad He II 4686A emission in the early spectrum of type II SN~2020jfo. The 4686A line is emitted presumably by dense fragments embedded into a hot gas of the forward shock wave. The fragments are produced as a result of a heavy braking of the dense low-mass shell at the ejecta boundary and a simultaneous Rayleigh-Taylor instability. The temperature of line-emitting fragments is $\approx$5$\times10^4$K. Calculations of ionization and excitation of helium and hydrogen account for the He II 4686A luminosity, the large flux ratio of He II 4686A/H$α$, and a significant optical depth of the 4686A line. We demonstrate that fragments heating by hot electrons behind the forward shock compensates cooling via the HeII 304A emission. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2402_18299 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Origin of broad He II 4686Å emission in early spectra of type IIP supernovae Chugai, Nikolai Utrobin, Victor High Energy Astrophysical Phenomena We propose a model for the origin of the broad He II 4686A emission in the early spectrum of type II SN~2020jfo. The 4686A line is emitted presumably by dense fragments embedded into a hot gas of the forward shock wave. The fragments are produced as a result of a heavy braking of the dense low-mass shell at the ejecta boundary and a simultaneous Rayleigh-Taylor instability. The temperature of line-emitting fragments is $\approx$5$\times10^4$K. Calculations of ionization and excitation of helium and hydrogen account for the He II 4686A luminosity, the large flux ratio of He II 4686A/H$α$, and a significant optical depth of the 4686A line. We demonstrate that fragments heating by hot electrons behind the forward shock compensates cooling via the HeII 304A emission. |
| title | Origin of broad He II 4686Å emission in early spectra of type IIP supernovae |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2402.18299 |