An Observational Study of Novae in Differing Stellar Populations

Allen Shafter博士将继续他在选定的邻近星系中对新星的空间分布、数量和爆发特性的研究。这项研究的主要动机是为了更深入地了解潜在的恒星群对紧密双星系统的形成、演化和物理特性的影响，特别是新星。新星非常适合这项任务，因为它们具有很高的光度，并且可以很容易地在跨越各种类型的星系中识别出来。基于标准新星形成场景的模型预测，与螺旋凸起和早期星系相比，具有年轻恒星人口组成的晚型星系的盘状成分应该是更多产的新星生产者（即，它们每单位质量的恒星应该有更多的新星爆发）。然而，现有的观测证据似乎与这一预测相矛盾，螺旋星系和椭圆星系的凸起似乎与年轻恒星群中的新星率一样高，甚至更高。如果得到证实，这些结果不仅会给恒星种群模型带来问题，而且会给目前最受欢迎的用于确定宇宙膨胀率的Ia型超新星祖先模型带来问题。这项研究的结果将与天文学中广泛的主题相关，从新星等近距离双星的形成和演化，到它们作为Ia型超新星的祖通道的潜在作用。来自圣地亚哥州立大学（SDSU）和SDSU本科生研究经验（REU）暑期项目的学生将直接参与这些新星的发现，测量它们的光谱，并确定它们的光学光的演变。

Dr. Allen Shafter will continue his study of the spatial distributions, populations, and outburst properties of novae in selected nearby galaxies. The principal motivation of the study is to acquire a deeper understanding of the effect that the underlying stellar population has on the formation, evolution, and physical properties of close binary systems in general, and novae in particular. Novae are ideally suited to this task because they have high luminosities and can be readily identified in galaxies spanning a wide range of types.Models based on standard nova formation scenarios predict that the disk components of late-type galaxies with their young stellar population component should be more prolific nova producers (i.e., they should have more nova eruptions per unit mass in stars) compared with spiral bulges and early-type galaxies. The available observational evidence, however, seems in conflict with this prediction, with the bulges of spirals and elliptical galaxies appearing to have nova rates as high, or higher, than that seen in younger stellar populations. If confirmed, these results create a problem not only for stellar population models, but for the currently favored model for the progenitors of Type Ia supernovae which are used to determine the expansion rate of the universe.The results of the study will be relevant to a wide range of topics in astronomy, from the formation and evolution of close binary stars such as novae, to their potential role as a progenitor channel for Type Ia supernovae. Students from San Diego State University (SDSU), and from SDSU's Research Experience for Undergraduates (REU) summer program, will be directly involved in the discovery of these novae, in measuring their spectra, and in determining the evolution of their optical light.