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arXiv · 1512.03995

A Luminous Peculiar Type Ia Supernova SN 2011hr: More Like SN 1991T or SN 2007if?

Jujia Zhang·Xiaofeng Wang·Michele Sasdelli·Tianmeng Zhang·Zhengweei Liu·Paolo A. Mazzali·Xiangcun Meng·Keiichi Maeda·Juncheng Chen·Fang Huang·Xulin Zhao·Kaicheng Zhang·Qian Zhai·Elena Pian·Bo Wang·Liang Chang·Weimin Yi·Chuan-Jun Wang·Xueli Wang·Yuxin Xin·Jianguo Wang·Baoli Lun·Xiangming Zheng·Xiliang Zhang·Yufeng Fan·Jinming Bai
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Abstract

Photometric and spectroscopic observations of a slowly declining, luminous Type Ia supernova (SN Ia) SN 2011hr in the starburst galaxy NGC 2691 are presented. SN 2011hr is found to peak at $M_{B}=-19.84 \pm 0.40\,\rm{mag}$, with a post-maximum decline rate $Δ$m$_{15}$(B) = 0.92 $\pm$ 0.03\,$\rm{mag}$. From the maximum-light bolometric luminosity, $L=(2.30 \pm 0.90) \times 10^{43}\,\rm{erg\,s^{-1}}$, we estimate the mass of synthesized \Nifs\ in SN 2011hr to be $M(\rm{^{56}Ni})=1.11 \pm 0.43\,M_{\sun}$. SN 2011hr appears more luminous than SN 1991T at around maximum light, and the absorption features from its intermediate-mass elements (IMEs) are noticeably weaker than the latter at similar phases. Spectral modeling suggests that SN 2011hr has the IMEs of $\sim$\,0.07 M$_{\sun}$ in the outer ejecta, which is much lower than the typical value of normal SNe Ia (i.e., 0.3 -- 0.4 M$_{\sun}$) and is also lower than the value of SN 1991T (i.e., $\sim$\,0.18 M$_{\sun}$). These results indicate that SN 2011hr may arise from a Chandrasekhar-mass white dwarf progenitor that experienced a more efficient burning process in the explosion. Nevertheless, it is still possible that SN 2011hr may serve as a transitional object connecting the SN 1991T-like SNe Ia with the superluminous subclass like SN 2007if given that the latter also shows very weak IMEs at all phases.

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Jujia Zhang, Xiaofeng Wang, Michele Sasdelli, Tianmeng Zhang, Zhengweei Liu, Paolo A. Mazzali, Xiangcun Meng, Keiichi Maeda, Juncheng Chen, Fang Huang, Xulin Zhao, Kaicheng Zhang, Qian Zhai, Elena Pian, Bo Wang, Liang Chang, Weimin Yi, Chuan-Jun Wang, Xueli Wang, Yuxin Xin, Jianguo Wang, Baoli Lun, Xiangming Zheng, Xiliang Zhang, Yufeng Fan, Jinming Bai. 2016-01-07. A Luminous Peculiar Type Ia Supernova SN 2011hr: More Like SN 1991T or SN 2007if?. https://doi.org/10.3847/0004-637x%2F817%2F2%2F114

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