Photospheric Velocity Gradients and Ejecta Masses of Hydrogen-poor Superluminous Supernovae: Proxies for Distinguishing between Fast and Slow Events
Photospheric Velocity Gradients and Ejecta Masses of Hydrogen-poor Superluminous Supernovae: Proxies for Distinguishing between Fast and Slow Events
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DOI：
10.3847/1538-4357/abd6c8
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发表时间：
2020-11
期刊：
影响因子：
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通讯作者：
R. Könyves-Tóth;J. Vinkó
中科院分区：
文献类型：
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作者：
R. Könyves-Tóth;J. Vinkó
我们在喷射物质量和光球速度的背景下对 28 颗 I 型超光度超新星 (SLSNe) 进行了研究。我们将光度测定和光谱学结合起来，通过辐射扩散方程的形式来推断喷射物的质量。我们提出了一种结合光谱建模和互相关技术来确定光球速度的改进方法。我们发现，I 型 SLSNe 根据其最大前光谱可以分为两组。第一组的成员在其最大前光谱中具有 W 形吸收谷，通常被认为是由 O ii 引起的。第二组超新星的光谱不存在这一特征，其光谱与 SN 2015bn 相似。我们确认前或接近最大的光球速度与速度梯度相关：演化速度较快的 SLSNe 在最大值附近具有较大的光球速度。我们根据所研究的 SLSNe 的估计光球速度将其分为快速演化组和慢速演化组，发现所有类似 SN 2015bn 的天体都属于慢速演化组，而表现出 W 状吸收的 SLSNe 在快速演化组和慢速演化组中都有代表。我们估计了样本中所有物体的喷射物质量，并获得了 2.9 (±0.8)−208 (±61) M ⊙ 范围内的值，平均值为 43 (±12) M ⊙ 。我们得出的结论是，与快速演化的 SLSNe 相比，缓慢演化的 SLSNe 往往具有更高的喷射物质量。我们的喷射物质量计算表明，无论光变曲线的动力机制如何，超大规模恒星爆炸都是由超大质量恒星的高能爆炸引起的。
We present a study of 28 Type I superluminous supernovae (SLSNe) in the context of the ejecta mass and photospheric velocity. We combine photometry and spectroscopy to infer ejecta masses via the formalism of radiation diffusion equations. We present an improved method to determine the photospheric velocity by combining spectrum modeling and cross-correlation techniques. We find that Type I SLSNe can be divided into two groups according to their pre-maximum spectra. Members of the first group have a W-shaped absorption trough in their pre-maximum spectrum, usually identified as due to O ii. This feature is absent in the spectra of supernovae in the second group, whose spectra are similar to that of SN 2015bn. We confirm that the pre- or near-maximum photospheric velocities correlate with the velocity gradients: faster evolving SLSNe have larger photospheric velocities around maximum. We classify the studied SLSNe into the Fast or the Slow evolving group according to their estimated photospheric velocities, and find that all those objects that resemble SN 2015bn belong to the Slow evolving class, while SLSNe showing the W-like absorption are represented in both Fast and Slow evolving groups. We estimate the ejecta masses of all objects in our sample, and obtain values in the range 2.9 (±0.8)−208 (±61) M ⊙, with a mean of 43 (±12) M ⊙. We conclude that Slow evolving SLSNe tend to have higher ejecta masses compared to the Fast SLSNe. Our ejecta mass calculations suggests that SLSNe are caused by energetic explosions of very massive stars, irrespective of the powering mechanism of the light curve.