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arXiv · 2301.09922

SN 2020uem: A Possible Thermonuclear Explosion within A Dense Circumstellar Medium (II) The Properties of The CSM from Polarimetry and Light Curve Modeling

Kohki Uno·Takashi Nagao·Keiichi Maeda·Hanindyo Kuncarayakti·Masaomi Tanaka·Koji S. Kawabata·Tatsuya Nakaoka·Miho Kawabata·Masayuki Yamanaka·Kentaro Aoki·Keisuke Isogai·Mao Ogawa·Akito Tajitsu·Ryo Imazawa
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Abstract

Type IIn/Ia-CSM supernovae (SNe IIn/Ia-CSM) are classified by their characteristic spectra, which exhibit narrow hydrogen emission lines originating from a strong interaction with a circumstellar medium (CSM) together with broad lines of intermediate-mass elements. We performed intensive follow-up observations of SN IIn/Ia-CSM 2020uem, including photometry, spectroscopy, and polarimetry. In this paper, we focus on the results of polarimetry. We performed imaging polarimetry at $66$ days and spectropolarimetry at $103$ days after the discovery. SN 2020uem shows a high continuum polarization of $1.0-1.5\%$ without wavelength dependence. Besides, the polarization degree and position angle keep roughly constant. These results suggest that SN 2020uem is powered by a strong interaction with a confined and aspherical CSM. We performed a simple polarization modeling, based on which we suggest that SN 2020uem has an equatorial-disk/torus CSM. Besides, we performed semi-analytic light-curve modeling and estimated the CSM mass. We revealed that the mass-loss rate in the final few hundred years immediately before the explosion of SN 2020uem is in the range of $0.01 - 0.05 {\rm ~M_{\odot}~yr^{-1}}$, and that the total CSM mass is $0.5-4 {\rm ~M_{\odot}}$. The CSM mass can be accommodated by not only a red supergiant (RSG) but a red giant (RG) or an asymptotic-giant-branch (AGB) star. As a possible progenitor scenario of SN 2020uem, we propose a white-dwarf binary system including an RG, RSG or AGB star, especially a merger scenario via common envelope evolution, i.e., the core-degenerate scenario or its variant.

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Kohki Uno, Takashi Nagao, Keiichi Maeda, Hanindyo Kuncarayakti, Masaomi Tanaka, Koji S. Kawabata, Tatsuya Nakaoka, Miho Kawabata, Masayuki Yamanaka, Kentaro Aoki, Keisuke Isogai, Mao Ogawa, Akito Tajitsu, Ryo Imazawa. 2023-01-24. SN 2020uem: A Possible Thermonuclear Explosion within A Dense Circumstellar Medium (II) The Properties of The CSM from Polarimetry and Light Curve Modeling. https://doi.org/10.3847/1538-4357%2Facb5eb

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