标题： SN Refsdal：被归类为明亮且蓝的类似SN 1987A的II型超新星 显示英文标题

标题： SN Refsdal: Classification as a Luminous and Blue SN 1987A-like Type II Supernova

摘要： 我们获得了哈勃太空望远镜（HST）和甚大望远镜（VLT）的近红外光谱和图像，观测对象是2014年秋季作为爱因斯坦十字发现的超新星（SN）Refsdal。 SN Refsdal的HST亮度曲线与SN 1987A型超新星（SNe）特有的缓慢上升亮度曲线相匹配，并且我们在螺旋星系宿主（红移z=1.49）的HST光栅光谱中发现了强烈的宽H-αP-Cygni谱线证据。 IIn型超新星，由周围物质相互作用驱动，可以很好地拟合SN Refsdal的亮度曲线，但IIn型超新星的光谱不会显示出宽而强的H-α吸收。 从光栅光谱中，我们测量出的H-α膨胀速度与相似阶段的SN 1987A型超新星的速度一致。 WFC3和X-shooter光谱中H-α发射的亮度、演化和高斯轮廓，在静止框架下相隔约2.5个月，提供了额外的证据支持SN 1987A型分类。 与其他SN 1987A型超新星的例子相比，SN Refsdal具有蓝色B-V颜色和假设范围内的高亮度。 如果SN Refsdal可以被建模为SN 1987A的缩放版本，我们估计它的喷出质量为20±5个太阳质量。 晚时间亮度曲线的演化将提供关于任何显著的周围物质（CSM）潜在存在的额外证据。 利用MOSFIRE和X-shooter光谱，我们估计爆炸附近的宿主星系金属丰度接近亚太阳水平（分别为8.3±0.1 dex和<8.4 dex）。 显示英文摘要

摘要： We have acquired Hubble Space Telescope (HST) and Very Large Telescope near-infrared spectra and images of supernova (SN) Refsdal after its discovery as an Einstein cross in Fall 2014. The HST light curve of SN Refsdal matches the distinctive, slowly rising light curves of SN 1987A-like supernovae (SNe), and we find strong evidence for a broad H-alpha P-Cygni profile in the HST grism spectrum at the redshift (z = 1.49) of the spiral host galaxy. SNe IIn, powered by circumstellar interaction, could provide a good match to the light curve of SN Refsdal, but the spectrum of a SN IIn would not show broad and strong H-alpha absorption. From the grism spectrum, we measure an H-alpha expansion velocity consistent with those of SN 1987A-like SNe at a similar phase. The luminosity, evolution, and Gaussian profile of the H-alpha emission of the WFC3 and X-shooter spectra, separated by ~2.5 months in the rest frame, provide additional evidence that supports the SN 1987A-like classification. In comparison with other examples of SN 1987A-like SNe, SN Refsdal has a blue B-V color and a high luminosity for the assumed range of potential magnifications. If SN Refsdal can be modeled as a scaled version of SN 1987A, we estimate it would have an ejecta mass of 20+-5 solar masses. The evolution of the light curve at late times will provide additional evidence about the potential existence of any substantial circumstellar material (CSM). Using MOSFIRE and X-shooter spectra, we estimate a subsolar host-galaxy metallicity (8.3+-0.1 dex and <8.4 dex, respectively) near the explosion site.