Systematic Investigation of Very-early-phase Spectra of Type Ia Supernovae
It has been widely accepted that Type Ia supernovae (SNe Ia) are thermonuclear explosions of a CO white dwarf. However, the natures of the progenitor system(s) and explosion mechanism(s) are still unclarified. Thanks to the recent development of transient observations, they are now frequently discov...
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| Format: | Article |
| Language: | English |
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IOP Publishing
2023-01-01
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| Series: | The Astrophysical Journal |
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| Online Access: | https://doi.org/10.3847/1538-4357/acec74 |
| _version_ | 1797683336582266880 |
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| author | Mao Ogawa Keiichi Maeda Miho Kawabata |
| author_facet | Mao Ogawa Keiichi Maeda Miho Kawabata |
| author_sort | Mao Ogawa |
| collection | DOAJ |
| description | It has been widely accepted that Type Ia supernovae (SNe Ia) are thermonuclear explosions of a CO white dwarf. However, the natures of the progenitor system(s) and explosion mechanism(s) are still unclarified. Thanks to the recent development of transient observations, they are now frequently discovered shortly after the explosion, followed by rapid spectroscopic observations. In this study, by modeling very-early-phase spectra of SNe Ia, we try to constrain the explosion models of SNe Ia. By using the Monte Carlo radiation transfer code, TARDIS, we estimate the properties of their outermost ejecta. We find that the photospheric velocity of normal-velocity supernovae (NV SNe) in the first week is ∼15,000 km s ^−1 . The outer velocity, to which the carbon burning extends, spans the range between ∼20,000 and 25,000 km s ^−1 . The ejecta density of NV SNe also shows a large diversity. For high-velocity supernovae (HV SNe) and 1999aa-like SNe, the photospheric velocity is higher, ∼20,000 km s ^−1 . They have different photospheric densities, with HV SNe having higher densities than 1999aa-like SNe. For all these types, we show that the outermost composition is closely related to the outermost ejecta density; the carbon-burning layer and the unburnt carbon layer are found in the higher-density and lower-density objects, respectively. This finding suggests that there might be two sequences, the high-density and carbon-poor group (HV SNe and some NV SNe) and the low-density and carbon-rich group (1999aa-like and other NV SNe), which may be associated with different progenitor channels. |
| first_indexed | 2024-03-12T00:12:56Z |
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| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-12T00:12:56Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-476c4747afbd42459e73b8741388eb5d2023-09-15T20:03:38ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0195514910.3847/1538-4357/acec74Systematic Investigation of Very-early-phase Spectra of Type Ia SupernovaeMao Ogawa0https://orcid.org/0000-0001-5822-1672Keiichi Maeda1https://orcid.org/0000-0003-2611-7269Miho Kawabata2https://orcid.org/0000-0002-4540-4928Department of Astronomy, Kyoto University , Kitashirakawa-Oiwake-Cho, Sakyo-ku, Kyoto, 606-8502, JapanDepartment of Astronomy, Kyoto University , Kitashirakawa-Oiwake-Cho, Sakyo-ku, Kyoto, 606-8502, JapanNishi-Harima Astronomical Observatory, Center for Astronomy, University of Hyogo , 407-2 Nishigaichi, Sayo-cho, Sayo, Hyogo, 679-5313, JapanIt has been widely accepted that Type Ia supernovae (SNe Ia) are thermonuclear explosions of a CO white dwarf. However, the natures of the progenitor system(s) and explosion mechanism(s) are still unclarified. Thanks to the recent development of transient observations, they are now frequently discovered shortly after the explosion, followed by rapid spectroscopic observations. In this study, by modeling very-early-phase spectra of SNe Ia, we try to constrain the explosion models of SNe Ia. By using the Monte Carlo radiation transfer code, TARDIS, we estimate the properties of their outermost ejecta. We find that the photospheric velocity of normal-velocity supernovae (NV SNe) in the first week is ∼15,000 km s ^−1 . The outer velocity, to which the carbon burning extends, spans the range between ∼20,000 and 25,000 km s ^−1 . The ejecta density of NV SNe also shows a large diversity. For high-velocity supernovae (HV SNe) and 1999aa-like SNe, the photospheric velocity is higher, ∼20,000 km s ^−1 . They have different photospheric densities, with HV SNe having higher densities than 1999aa-like SNe. For all these types, we show that the outermost composition is closely related to the outermost ejecta density; the carbon-burning layer and the unburnt carbon layer are found in the higher-density and lower-density objects, respectively. This finding suggests that there might be two sequences, the high-density and carbon-poor group (HV SNe and some NV SNe) and the low-density and carbon-rich group (1999aa-like and other NV SNe), which may be associated with different progenitor channels.https://doi.org/10.3847/1538-4357/acec74Type Ia supernovaeRadiative transfer simulationsWhite dwarf stars |
| spellingShingle | Mao Ogawa Keiichi Maeda Miho Kawabata Systematic Investigation of Very-early-phase Spectra of Type Ia Supernovae The Astrophysical Journal Type Ia supernovae Radiative transfer simulations White dwarf stars |
| title | Systematic Investigation of Very-early-phase Spectra of Type Ia Supernovae |
| title_full | Systematic Investigation of Very-early-phase Spectra of Type Ia Supernovae |
| title_fullStr | Systematic Investigation of Very-early-phase Spectra of Type Ia Supernovae |
| title_full_unstemmed | Systematic Investigation of Very-early-phase Spectra of Type Ia Supernovae |
| title_short | Systematic Investigation of Very-early-phase Spectra of Type Ia Supernovae |
| title_sort | systematic investigation of very early phase spectra of type ia supernovae |
| topic | Type Ia supernovae Radiative transfer simulations White dwarf stars |
| url | https://doi.org/10.3847/1538-4357/acec74 |
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