Galactic Novae: Thinking Inside the Envelope

1. 新星是一颗因较大因素突然变亮的恒星。一些新星的亮度可能达到太阳的数万倍。快速变亮是由一颗白矮星表面失控的热核爆炸引起的；它是一颗体积和地球一样大，质量和太阳差不多的小恒星。白矮星从一颗普通的恒星中积累氢，为新星爆发提供燃料，这颗恒星是白矮星的亲密伴侣。爆炸从白矮星表面喷射出大量物质，使空间充满了热核爆炸过程中产生的重元素。尽管新星自古以来就为人所知，而且天体物理学家自上世纪中叶以来就已经了解了新星爆炸的原因，但重要的谜团仍然存在。在过去的几年里，宇宙飞船的观测显示，至少有一些新星发射出非常高能的伽马射线。这是出乎意料的，至今仍是个谜。一些新星也可能是Ia型超新星的前身，这对宇宙学具有重要意义。首席研究员将对他在过去14年中积累的83颗新星的观测数据图谱进行广泛的科学分析。这项研究将解决关于新星的几个关键问题。调查的结果构成了这个项目的智力价值。更广泛的影响源于PI建议本科生和高中生直接参与研究。他指出，自1991年以来，他指导的五名高中生进入了英特尔科学人才搜索大赛的半决赛。PI还将与美国变星观测者协会（AAVSO）合作，以提高参与的业余观测者的经验。新星爆发是由白矮星上吸积H层简并底部的热核失控引起的。氢层是由一个紧密的双星伴星的质量传递积累而成的。在爆发期间，新星的亮度增加，在某些情况下达到太阳亮度的数万倍。一颗新星的爆炸将相当于太阳质量万分之一的白矮星喷射到星际介质中，使其富含核燃烧过程中产生的重元素。在过去的几年里，费米伽马射线天文台发现一些新星发射高能伽马辐射；这些排放物的来源仍不清楚。一些新星也可能是Ia型超新星的前体，这对宇宙学具有重要意义。为了解决这些爆发变量的几个关键问题，首席研究员将对他在过去14年中积累的83颗新星的高节奏光度和光谱数据进行详尽的科学分析。这些调查的结果构成了这个项目的智力价值。更广泛的影响源于PI建议本科生和高中生直接参与研究。他指出，自1991年以来，他指导的五名高中生进入了英特尔科学人才搜索大赛的半决赛。PI还将与美国变星观测者协会（AAVSO）合作，以提高参与的业余观测者的经验。

1. A nova is a star that brightens abruptly by a large factor. Some novae may become as much as tens of thousands of times brighter than our Sun. The rapid brightening is caused by a runaway thermonuclear explosion on the surface of a white dwarf star; a small star that packs about as much mass as our Sun into a volume the size of Earth. The white dwarf accumulates the hydrogen that fuels the nova outburst from an ordinary star that is a close companion. The explosion ejects mass from the surface of the white dwarf, enriching space with heavier elements produced during the thermonuclear explosion. Although novae have been known since ancient times, and astrophysicists have understood the cause of a nova explosion since the middle of the last century, important puzzles still remain. Over the past several years, spacecraft observations have revealed that at least some novae emit very high-energy gamma radiation. This was unexpected and is still mysterious. Some novae also may be progenitors of Type Ia supernovae, which have significant implications for cosmology. The Principal Investigator will conduct extensive scientific analyses of the atlas of observational data he has accumulated for 83 novae over the past 14 years. This research will address several key questions about novae. The results of the investigations constitute the Intellectual Merit of this project. The Broader Impacts stem from the PI's proposed involvement of undergraduates and high-school students directly in the research. He points out that since 1991, five of the high-school students he has supervised have been semi-finalists in the Intel Science Talent Search. The PI will also collaborate with the American Association of Variable Star Observers (AAVSO) to enhance the experiences of participating amateur observers.2. Nova eruptions are caused by thermonuclear runaways at the degenerate base of an accreted H layer on a white dwarf. The hydrogen layer is accumulated by mass transfer from a close binary companion star. During outburst, a nova increases in brightness, in some cases reaching tens of thousands of times the luminosity of the Sun. A nova explosion ejects as much one ten-thousandth of a solar mass from the white dwarf into the interstellar medium, enriching it in heavier elements produced in the nuclear burning event. During the past several years, the Fermi Gamma Ray Observatory has discovered that some novae emit high-energy gamma radiation; the origin of these emissions is still not well understood. Some novae also may be the precursors of Type Ia supernovae, which have important implications for cosmology. In order to address several key questions about these eruptive variables, the Principal Investigator will conduct exhaustive scientific analyses of the atlas of high-cadence photometric and spectroscopic data he has accumulated for 83 novae over the past 14 years. The results of these investigations constitute the Intellectual Merit of this project. The Broader Impacts stem from the PI's proposed involvement of undergraduates and high-school students directly in the research. He points out that since 1991, five of the high-school students he has supervised have been semi-finalists in the Intel Science Talent Search. The PI will also collaborate with the American Association of Variable Star Observers (AAVSO) to enhance the experiences of participating amateur observers.