SN 2016gsd: An unusually luminous and linear type II supernova with high velocities
T. M. Reynolds, M. Fraser, S. Mattila, M. Ergon, P. Lundqvist, L. Dessart, Subo Dong, N. Elias-Rosa, L. Galbany, C. P. Gutiérrez, T. Kangas, E. Kankare, R. Kota… 展开作者
T. M. Reynolds, M. Fraser, S. Mattila, M. Ergon, P. Lundqvist, L. Dessart, Subo Dong, N. Elias-Rosa, L. Galbany, C. P. Gutiérrez, T. Kangas, E. Kankare, R. Kotak, H. Kuncarayakti, A. Pastorello, O. Rodriguez, S. J. Smartt, M. Stritzinger, L. Tomasella, Ping Chen, J. Harmanen, G. Hozzeinzadeh, D. Andrew Howell, C. Inserra, M. Nicholl, M. Nielsen, K. Smith, A. Somero, R. Tronsgaard, D. R. Young
备注：
25 pages, 17 figures, Published by MNRAS. Re-uploaded to reflect published version. Changes made to Figures 1,8,11 to give more information, new figure 15 added. Changes to text to improve clarity and add additional information and analysis requested by the referee
我们目前的观测异常明亮的II型超新星（SN）2016gsd。该天体的峰值绝对星等为V = $-$ 19.95 $\pm$ 0.08，是最亮的II型超新星之一，位于大多数II型超新星和超亮超新星之间的星等差距。它的光变曲线几乎没有显示出从光学厚相到放射性动力尾部的预期下降的证据。从H $α$的吸收导出的速度也异常高，蓝边跟踪最快移动的气体，最初在20000 km s $^{-1}$，然后近似线性下降到15000 km s $^{-1}$超过$\sim$ 100 d。SN的矮宿主星系表明低金属量的祖先，这也可能有助于其光谱中的金属线的弱点。我们研究SN 2016gsd与类似的发光，线性II型SNe，如SNe 1979C和1998S，并讨论其观测特征的解释。我们将观测结果与JEKYLL代码生成的模型进行比较，发现一颗具有耗尽和膨胀氢包层的大质量恒星正在努力重现SN 2016gsd的高光度和极端线性。相反，我们认为，SN喷出物和拱星材料之间的相互作用的影响可以解释大多数观察到的SN属性。在SN的整个演化过程中存在的高速度和强H $α$吸收可能意味着一种配置在非对称几何形状中的星周介质。
英文摘要：
We present observations of the unusually luminous Type II supernova (SN) 2016gsd. With a peak absolute magnitude of V = $-$19.95 $\pm$ 0.08, this object is one of the brightest Type II SNe, and lies in the gap of magnitudes between the majority of Type II SNe and the superluminous SNe. Its light curve shows little evidence of the expected drop from the optically thick phase to the radioactively powered tail. The velocities derived from the absorption in H$α$ are also unusually high with the blue edge tracing the fastest moving gas initially at 20000 km s$^{-1}$, and then declining approximately linearly to 15000 km s$^{-1}$ over $\sim$100 d. The dwarf host galaxy of the SN indicates a low-metallicity progenitor which may also contribute to the weakness of the metal lines in its spectra. We examine SN 2016gsd with reference to similarly luminous, linear Type II SNe such as SNe 1979C and 1998S, and discuss the interpretation of its observational characteristics. We compare the observations with a model produced by the JEKYLL code and find that a massive star with a depleted and inflated hydrogen envelope struggles to reproduce the high luminosity and extreme linearity of SN 2016gsd. Instead, we suggest that the influence of interaction between the SN ejecta and circumstellar material can explain the majority of the observed properties of the SN. The high velocities and strong H$α$ absorption present throughout the evolution of the SN may imply a circumstellar medium configured in an asymmetric geometry.
