We present a survey of the early evolution of 12 Type IIn supernovae (SNe IIn) in the Ultra-Violet (UV) and visible light. We use this survey to constrain the geometry of the circumstellar material (CSM) surrounding SN IIn explosions, which may shed light on their progenitor diversity. In order to distinguish between aspherical and spherical circumstellar material (CSM), we estimate the blackbody radius temporal evolution of the SNe IIn of our sample, following the method introduced by Soumagnac et al. We find that higher luminosity objects tend to show evidence for aspherical CSM. Depending on whether this correlation is due to physical reasons or to some selection bias, we derive a lower limit between 35% and 66% on the fraction of SNe IIn showing evidence for aspherical CSM. This result suggests that asphericity of the CSM surrounding SNe IIn is common - consistent with data from resolved images of stars undergoing considerable mass loss. It should be taken into account for more realistic modelling of these events.

中文翻译：

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IIn 型超新星的早期紫外观测限制了其环绕恒星物质的非球面性

我们在紫外线 (UV) 和可见光下对 12 颗 IIn 型超新星 (SNe IIn) 的早期演化进行了调查。我们使用这项调查来限制围绕 SN IIn 爆炸的星周物质 (CSM) 的几何形状，这可能会揭示它们的祖先多样性。为了区分非球面和球面星周物质（CSM），我们按照 Soumagnac 等人介绍的方法估计了我们样本的 SNe IIn 的黑体半径时间演化。我们发现更高光度的物体倾向于显示非球面 CSM 的证据。根据这种相关性是由于物理原因还是由于某些选择偏差，我们得出了显示非球面 CSM 证据的 SNe IIn 分数的 35% 到 66% 之间的下限。这一结果表明，围绕 SNe IIn 的 CSM 的非球面性是常见的——与来自经历大量质量损失的恒星的解析图像的数据一致。应该考虑对这些事件进行更真实的建模。