Collaborative Research: Mapping the Supernova Polarization Landscape

超新星，或大质量恒星的爆炸，对于理解它至关重要，因为它们产生并分散了组成行星和生命的许多原子元素，也因为它们在整个宇宙中的亮度被用来测量宇宙的膨胀。超新星(SN)爆炸不是球形的，而是几何上复杂的现象，随着爆炸的演变，其非球面结构会导致观测到的特征发生变化。丹佛大学(DU)和圣地亚哥州立大学(SDSU)之间的一项研究合作使用了一种名为光谱偏振的观测技术来提供有关SNE的详细三维信息，探测无法从地球甚至太空直接成像的空间尺度。光谱偏振法将探测来自超新星的光的偏振与测量该光的光谱相结合。这些信息揭示了喷射物中密度、温度和光照模式随时间的变化；并为爆炸机制和前驱系统的性质提供了线索。该项目将通过培训学生进行这些类型的观察和建模来推进发现的未来。它还将有助于培训未来多样化的STEM社区。调查人员将开发一个实践学习模块，演示两极分化的概念，直接融入两项活动：由杜克大学首席调查员(PI)共同指导的DU科技夏令营，每年将有色人种中学女孩带到校园参加为期一周的基于发现的STEM夏令营，以及由SDSU PI领导的广泛外展活动。科学家们将使用超新星光谱偏振项目(SNSPOL)从2011年到2018年收集的数据，该项目是现有的所有类型的SNE光谱偏振观测的最大数据库，其中包括106个所有类型的SNE，其中50个是在3+个历元观测到的。他们将使用最先进的建模技术来解释这些数据。观测调查发现超新星和相关的瞬变正在以越来越快的速度增长。该项目将扩大这些发现的科学影响，极大地扩大现有的用分光偏振法检查的SNE的目录，并定量地建立每种SN类型的共同特征。SNSPOL数据库中的多历元观测随着光球层的消退追踪每个SN的演化，对喷出物进行更深入的探索，并揭示爆炸本身的本质线索。从这些数据中提取和分析最显著的光谱偏振特征将使它们所包含的丰富信息可供未来的研究人员使用。这一结果将建立对所有类型的近地天体的3D本质的更全面的理解，并形成恒星爆炸模型的关键判别式。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Supernovae, or the explosions of massive stars, are critical to understand, both because they produce and disperse many of the atomic elements that make up planets and life, and because their brightness throughout the Universe is used to measure the expansion of the Universe. Supernova (SN) explosions are not spherical, but rather geometrically complex phenomena, whose aspherical structures cause variations in observed characteristics over time as the explosion evolves. A research collaboration between the University of Denver (DU) and San Diego State University (SDSU) uses an observational technique called spectropolarimetry to provide detailed three-dimensional information about SNe, probing spatial scales that cannot be resolved through direct imaging from earth or even from space. Spectropolarimetry combines detection of the polarization of light from a supernova with measurement of the spectrum of that light. This information reveals the changing densities, temperatures, and illumination patterns in the ejecta over time; and gives clues to the explosion mechanisms and the nature of progenitor systems. The project will advance the future of discovery by training students in these types of observations and modeling. It will also contribute to the training of a future diverse STEM community. The investigators will develop a hands-on learning module demonstrating the concept of polarization, for direct integration into two activities: the DU SciTech camp, co-directed by the DU principal investigator (PI), which brings middle-school girls of color to campus for a week-long discovery-based STEM camp each year, and also the extensive outreach activities led by the SDSU PI. The scientists will use data collected from 2011 to 2018 by the Supernova Spectropolarimetry (SNSPOL) Project, the largest existing database of spectropolarimetric observations of SNe of all types, which includes 106 SNe of all types, with 50 observed at 3+ epochs. They will interpret these data with new state-of-the-art modeling techniques. Observational surveys are discovering supernovae and related transients at an ever-increasing rate. The project will broaden the scientific impact of these discoveries by greatly expanding the existing catalog of SNe examined with spectropolarimetry and quantitatively establishing the common signatures of each SN type. The multi-epoch observations in the SNSPOL database trace each SN’s evolution as the photosphere recedes, probing ever deeper into the ejecta and revealing clues to the very nature of the explosion itself. Extracting and analyzing the most salient spectropolarimetric features from these data will make the wealth of information they contain available to future researchers. The results will build a fuller understanding of the 3D nature of SNe of all types and form a key discriminant for stellar explosion models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.