Constraining Type Ia Supernova Progenitors via their Environments

超新星（SNe）或恒星爆炸是重要的天文事件，原因有很多：它们产生重原子元素并将其分布到星系中，它们可以作为距离遥远星系的指标，这对研究宇宙学至关重要。 超新星科学中一个尚未解决的主要问题是爆炸的起源。 密歇根州立大学（MSU）的一个研究小组将试图通过调查超新星周围的星周介质（CSM）来更好地了解SNe。CSM记录了爆炸前数千年的质量损失历史，因此是确定SN祖先的关键。 研究人员将重点探测与SN喷出物撞击CSM壳的相互作用冲击相关的紫外（UV）波长的原子线发射。 他们将使用紫外线图像档案数据库和解释的背景下，已公布的壳相互作用模型派生的通量。 作为该项目的一部分，研究人员将与密歇根州立大学的Charles Drew科学学者计划和国家天文学联盟合作，让来自不同背景的本科生参与超新星科学的夏季和学年研究。单简并通道（主序星/红巨星伴星）和双简并通道（白色矮伴星）是两种主要的祖先通道假说。近年来，超新星Ia被发现带有CSM的分离壳，其喷出物在爆炸后数月或数年撞击（即，延迟交互）。这种物质的来源是未知的，但有两种可能的可能性可以区分祖通道。在单简并通道中，SN之前可能有多个新星爆发，可以形成亚太阳质量的壳层，而在双简并通道中，SN之前排出一个共同的包层，形成一个少太阳质量的壳层。 研究人员将寻找更多的延迟相互作用SNe Ia的例子，并使用适当的理论框架来确定分离的CSM壳的性质范围。 他们将在已发表的壳层相互作用模型的背景下解释导出的通量，并将计算来自模型的UV和光学发射线信号，以产生光变曲线的网格，其亮度和持续时间取决于CSM的质量，半径，范围和几何形状。通过将这些模拟的光变曲线与数据进行比较，他们将计算SNe Ia在一系列CSM属性中托管CSM壳的概率。这将提供最严格的限制的存在和属性CSM外壳周围SNe Ia到目前为止，并提供一个严格的测试的假设，SNe Ia可以发生，而弹出的公共信封仍然在系统中。这个奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的知识价值和更广泛的影响审查标准。

Supernovae (SNe), or stellar explosions, are important astronomical events for many reasons: they produce and distribute heavy atomic elements into the galaxy, and they can be used as indicators of distances to far-away galaxies, which is vital for studying cosmology. One of the major unsolved problems in supernova science is the nature of the progenitor of the explosion. A research group at Michigan State University (MSU) will attempt to better understand SNe by investigating the circumstellar medium (CSM) around supernovae. The CSM records the history of mass-loss in the millennia prior to explosion, and therefore is a key to determining SN progenitors. The investigators will focus on detecting atomic line emission at ultraviolet (UV) wavelengths associated with the interaction shock from SN ejecta impacting a CSM shell. They will use UV image archival databases and interpret derived fluxes in the context of published shell-interaction models. As part of the project, the researchers will work with the Charles Drew Science Scholars program at MSU and the National Astronomy Consortium to involve undergraduate students from diverse backgrounds in summer and academic year research in supernova science.For Type Ia SNe, the CSM can reveal the identity of the mass-donor companion, which reveals the physics of both the binary interaction and supernova explosion. The single-degenerate (main sequence/red giant companion) and double-degenerate (white dwarf companion) channels are two dominant progenitor hypotheses. In recent years, SNe Ia have been discovered with detached shells of CSM that the ejecta impact months or years after explosion (i.e., delayed interaction). The origin of this material is unknown, but there are two likely possibilities which can distinguish between progenitor channels. In the single-degenerate channel, a SN may be preceded by multiple nova eruptions, which can form sub-solar-mass shells—while in the double-degenerate channel, a common envelope is expelled before the SN, forming a few-solar-mass shell. The investigators will search for more examples of delayed-interaction SNe Ia and use an appropriate theoretical framework to determine the range of properties of detached CSM shells. They will interpret derived fluxes in the context of published shell-interaction models, and will calculate the UV and optical emission line signals from the models to produce a grid of light curves whose luminosity and duration depend on the CSM mass, radius, extent, and geometry. By comparing these simulated light curves to data, they will calculate the probability of SNe Ia hosting CSM shells across a range of CSM properties. This will provide the most stringent constraints on the presence and properties of CSM shells around SNe Ia to date, and provide a rigorous test of the hypothesis that SNe Ia can occur while the ejected common envelope is still in the system.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.