Origin of High-velocity Ejecta, Excess Emission, and Redward Color Evolution in the Infant Type Ia Supernova 2021aefx

Abstract SN 2021aefx is a normal Type Ia supernova (SN) showing excess emission and redward color evolution over the first ∼ 2 days. We present analyses of this SN using our high-cadence KMTNet multiband photometry, spectroscopy, and publicly available data, including first measurements of its explo...

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Bibliographic Details
Published in:The Astrophysical journal 2023-12, Vol.959 (2), p.132
Main Authors: Ni, Yuan Qi, Moon, Dae-Sik, Drout, Maria R., Matzner, Christopher D., Leong, Kelvin C. C., Kim, Sang Chul, Park, Hong Soo, Lee, Youngdae
Format: Article
Language:English
Subjects:
Astrophysics
Binary stars
Ejecta
Emissions
Evolution
Explosions
Photosphere
Power sources
Spectroscopy
Spectrum analysis
Supernova
Supernovae
Time domain astronomy
Transient sources
Type Ia supernovae
Velocity
White dwarf stars
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Summary:Abstract SN 2021aefx is a normal Type Ia supernova (SN) showing excess emission and redward color evolution over the first ∼ 2 days. We present analyses of this SN using our high-cadence KMTNet multiband photometry, spectroscopy, and publicly available data, including first measurements of its explosion epoch (MJD 59529.32 ± 0.16) and onset of power-law rise ( t PL = MJD 59529.85 ± 0.55; often called first light ) associated with the main ejecta 56 Ni distribution. The first KMTNet detection of SN 2021aefx precedes t PL by ∼ 0.5 hr, indicating presence of additional power sources. Our peak-spectrum confirms its intermediate Type Ia subclassification between core-normal and broad-Line, and we estimate an ejecta mass of ∼ 1.34 M ⊙ . The spectral evolution identifies material reaching >40,000 km s −1 (fastest ever observed in Type Ia SNe) and at least two split-velocity ejecta components expanding homologously: (1) a normal-velocity (∼ 12,400 km s −1 ) component consistent with typical photospheric evolution of near-Chandrasekhar-mass ejecta; and (2) a high-velocity (∼ 23,500 km s −1 ) secondary component visible during the first ∼ 3.6 days post-explosion, which locates the component within the outer
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ad0640