Abstract
Abstract In this Letter we report a discovery of a prominent flash of a peculiar overluminous Type Ia supernova, SN 2020hvf, in about 5 hr of the supernova explosion by the first wide-field mosaic CMOS sensor imager, the Tomo-e Gozen Camera. The fast evolution of the early flash was captured by intensive intranight observations via the Tomo-e Gozen high-cadence survey. Numerical simulations show that such a prominent and fast early emission is most likely generated from an interaction between 0.01 M ⊙ circumstellar material (CSM) extending to a distance of ∼1013 cm and supernova ejecta soon after the explosion, indicating a confined dense CSM formation at the final evolution stage of the progenitor of SN 2020hvf. Based on the CSM–ejecta interaction-induced early flash, the overluminous light curve, and the high ejecta velocity of SN 2020hvf, we suggest that the SN 2020hvf may originate from a thermonuclear explosion of a super-Chandrasekhar-mass white dwarf (“super-M Ch WD”). Systematical investigations on explosion mechanisms and hydrodynamic simulations of the super-M Ch WD explosion are required to further test the suggested scenario and understand the progenitor of this peculiar supernova.
Highlights
Type Ia supernovae (SNe Ia) are widely believed to be the thermonuclear explosion of a white dwarf (WD; e.g., Hillebrandt & Niemeyer 2000, Hoeflich 2017, Nomoto &Leung 2017, Nomoto & Leung 2018)
BVRIJHKs-band imaging observations were performed with the Hiroshima One-shot Wide-field Polarimeter (HOWPol; Kawabata et al 2008) and Hiroshima Optical and Near-InfraRed camera (HONIR; Akitaya et al 2014) installed on the Nasmyth and the Cassegrain foci of the Kanata telescope, respectively
The early-phase light curves are computed with SNEC as in the same manner as with the circumstellar material (CSM)–ejecta interaction model
Summary
Type Ia supernovae (SNe Ia) are widely believed to be the thermonuclear explosion of a white dwarf By applying a simple “super-MCh” WD progenitor explosion with the CSM-interaction early-excess scenario, observational characteristics of the SN 2020hvf including the prompt earlyflash and overluminous light curves can be explained reasonably well. A prominent brightening in the first few days of the explosion can be observed in UV and optical wavelengths under specific viewing directions due to the interaction between the expanding ejecta and a nondegenerate companion star, which makes SNe Ia with additional luminosity enhancement in the early time a powerful indicator of the singledegenerate progenitor scenario (Kasen 2010; Maeda et al 2014; Kutsuna & Shigeyama 2015). Among the previously discovered early-excess SNe. Ia, two carbon-rich overluminous SNe Ia, LSQ12gpw (Jiang et al.2018) and ASASSN-15pz (Chen et al 2019), likely show earlyexcess features while inadequate early-phase photometries prevent
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