Title: Optical and Ultraviolet Observations of the Narrow-Lined Type Ia SN 2012fr in NGC 1365 Show Chinese title

Title: 窄线型Ia型超新星2012fr在NGC 1365中的光学和紫外观测

Abstract: Extensive optical and ultraviolet (UV) observations of the type Ia supernova (SN Ia) 2012fr are presented in this paper. It has a relatively high luminosity, with an absolute $B$-band peak magnitude of about $-19.5$ mag and a smaller post-maximum decline rate than normal SNe Ia [e.g., $\Delta m _{15}$($B$) $= 0.85 \pm 0.05$ mag]. Based on the UV and optical light curves, we derived that a $^{56}$Ni mass of about 0.88 solar masses was synthesized in the explosion. The earlier spectra are characterized by noticeable high-velocity features of \ion{Si}{2} $\lambda$6355 and \ion{Ca}{2} with velocities in the range of $\sim22,000$--$25,000$ km s$^{-1}$. At around the maximum light, these spectral features are dominated by the photospheric components which are noticeably narrower than normal SNe Ia. The post-maximum velocity of the photosphere remains almost constant at $\sim$12,000 km s$^{-1}$ for about one month, reminiscent of the behavior of some luminous SNe Ia like SN 1991T. We propose that SN 2012fr may represent a subset of the SN 1991T-like SNe Ia viewed in a direction with a clumpy or shell-like structure of ejecta, in terms of a significant level of polarization reported in Maund et al. (2013). Show Chinese abstract

Abstract: 本文介绍了对类型Ia超新星(SN Ia) 2012fr的广泛光学和紫外(UV)观测。它的光度相对较高，绝对$B$-band 峰值星等约为$-19.5$星等，且最大亮度后的衰减率比正常SNe Ia更小 [例如，$\Delta m _{15}$($B$) $= 0.85 \pm 0.05$ mag]。根据紫外和光学光变曲线，我们推导出在爆炸中合成了约0.88个太阳质量的$^{56}$Ni。 早期光谱表现出明显的高速特征，如\ion{Si}{2} $\lambda$ 6355 和\ion{Ca}{2}，其速度范围在$\sim22,000$--$25,000$km s$^{-1}$。 在光极大附近，这些光谱特征由光球层成分主导，明显比正常的 Ia 型超新星更窄。 光球的最大速度在大约一个月内几乎保持不变，为$\sim$12,000 km s$^{-1}$，类似于一些明亮的 Ia 型超新星如 SN 1991T 的行为。 我们提出，SN 2012fr 可能代表了 SN 1991T 类似 Ia 型超新星的一个子集，从具有团块状或壳层状抛射物结构的方向观测到的显著偏振水平，如 Maund 等人 (2013) 所报告的那样。