论文标题
超浮肿超新星SN 2017EGM的晚期光谱学观测值探测内部喷射的几何形状
Late-Phase Spectropolarimetric Observations of Superluminous Supernova SN 2017egm to Probe the Geometry of the Inner Ejecta
论文作者
论文摘要
我们在附近的Galaxy NGC 3191中介绍了SN 2017EGM的光谱观察结果，SN 2017EGM是I型超浮肿的超新星（SLSN-I），在G波段最大光后的185.0天，Subaru望远镜在最大光线后的185.0天。这是晚期SLSNE的第一个光谱图。我们发现晚期极化程度与早期测量的极化变化显着变化。晚期的光谱显示出强大的Ca发射线，因此我们可靠地估计了星际极化成分，假设发射线本质上是脱光化的。通过减去估计的星际极化，我们发现早期的内在极化仅为〜0.2％，这表明几乎是球形的光球，轴向比率〜1.05。晚期的固有极化增加到〜0.8％，与轴向比率为1.2的光球相对应。极化的几乎恒定的位置角表明内部喷射几乎是轴对称的。通过这些观察结果，我们得出结论，内部喷射比外射流更界外。它可能表明存在产生非球体内部喷射的中央能源。
We present our spectropolarimetric observations of SN 2017egm, a Type I superluminous supernova (SLSN-I) in a nearby galaxy NGC 3191, with Subaru telescope at 185.0 days after the g-band maximum light. This is the first spectropolarimetric observation for SLSNe at late phases. We find that the degree of the polarization in the late phase significantly changes from that measured at the earlier phase. The spectrum at the late phase shows a strong Ca emission line and therefore we reliably estimate the interstellar polarization component assuming that the emission line is intrinsically unpolarized. By subtracting the estimated interstellar polarization, we find that the intrinsic polarization at the early phase is only ~ 0.2 %, which indicates an almost spherical photosphere, with an axial ratio ~ 1.05. The intrinsic polarization at the late phase increases to ~ 0.8 %, which corresponds to the photosphere with an axial ratio 1.2. A nearly constant position angle of the polarization suggests the inner ejecta are almost axisymmetric. By these observations, we conclude that the inner ejecta are more aspherical than the outer ejecta. It may suggest the presence of a central energy source producing aspherical inner ejecta.
