Explosions on Accreting White Dwarfs: From Novae to Supernovae

该项目的重点是更好地了解从恒星伴星到白色矮星表面上的物质的点燃。直到一颗吸积中的白色矮星最后爆发为Ia型超新星，质量转移最明亮的表现是物质吸积壳的热核点火。对于氢供体，这些是经典新星;对于氦供体，这些是He新星或弱表面爆炸。观测这些闪光提供了一个遥远星系中这类双星数量的普查。在这里，将进行吸积白色矮星表面爆炸的理论工作，特别是考虑一系列新的环境，从纯氦吸积到碳/氧白色矮星到富氢吸积到纯氦白色矮星。 光学瞬变巡天（如Pan-STARRS-1、Pan-STARRS-4、SkyMapper、大型综合巡天望远镜）在数量和质量上即将取得的进展，以及对银河系双星的详细X射线和光学研究，使得这些理论研究的时机已经成熟。两个特定的领域将被调查。一：来自AM犬双星的氦爆炸。在这些短轨道周期（60分钟）的双星中，氦吸积到碳/氧白色矮星上，经历了一系列不稳定的闪光，产生了一系列令人兴奋的结果，从氦经典新星到爆炸，导致暗淡的Ia型超新星。对一个1000亿太阳质量的椭圆星系的初始速率估计，氦新星每25年发生一次，放射性氦爆炸每1000年发生一次（Ia型超新星速率的10%）。二：吸积中的白色矮星上氢燃烧的新机制。对Ia型超新星起源的理解，很大一部分与在吸积白色矮星上以吸积速率燃烧吸积氢的能力有关。然而，当不稳定时，在快速吸积速率下不稳定点火的实际热核触发器可以取决于吸积物质的金属丰度，产生遥远星系的经典新星速率，这取决于宿主恒星人口的质量和金属丰度。此外，氦白色矮星在质量转移双星中作为吸积体的作用一直是一个长期存在的难题。初步迹象表明，在这些寒冷的低重力天体上，不稳定的氢燃烧闪光所需的质量将非常大，可能为像M31那样的爆发提供理想的环境。预计这项工作将激发对遥远星系的新的瞬态调查。此外，参与该项目的研究生将接受理论，数值建模和数据采集方面的培训。PI将继续加速将拉斯坎布雷斯天文台全球望远镜网络纳入国际天体物理学界。为当地外联讲解员制定K-12天文学课程将加强他们的努力，特别是在代表性不足的少数民族中。

This project is focused on developing a better understanding of the ignition of matter accreted from stellar companions onto the surfaces of white dwarfs. Until the final explosion of an accreting white dwarf as a Type Ia supernova, the brightest manifestations of mass transfer are the thermonuclear ignitions of accreted shells of matter. With Hydrogen donors, these are Classical Novae; with Helium donors, these are He novae or weak surface explosions. Observing these flashes provides a census of the numbers of such binaries in distant galaxies. Here, theoretical work on surface explosions on accreting white dwarfs will be undertaken, specifically considering a range of new environments, from pure Helium accretion onto a Carbon/Oxygen white dwarf to Hydrogen-rich accretion onto a pure Helium white dwarf. The upcoming advances in the number and quality of optical transient surveys (e.g. Pan-STARRS-1, Pan-STARRS-4, SkyMapper, Large Synoptic Survey Telescope) and the detailed x-ray and optical studies of binaries in the Milky Way makes the time ripe for these theoretical studies. Two specific areas will be investigated.One: Helium Explosions from AM Canum Venaticorum Binaries. The Helium that accretes onto a Carbon/Oxygen white dwarf in these short orbital period ( 60 minute) binaries undergoes a series of unstable flashes with an exciting range of outcomes, from He Classical Novae to explosions leading to faint Type Ia supernovae. Initial rate estimates for a 100 billion solar mass elliptical galaxy give Helium Novae at a rate of one every 25 years and a radioactive He explosion every 1000 years ( 10% of the Type Ia supernovae rate).Two: New Regimes of Hydrogen Burning on Accreting White Dwarfs. A large part of the understanding of the origin of Type Ia supernovae is connected to the ability to burn accreted Hydrogen on an accreting white dwarf at the rate accreted. However, when unstable, the actual thermonuclear trigger for the unstable ignition at rapid accretion rates can depend on the metallicity of the accreted material, yielding Classical Novae rates for distant galaxies that depend on both the mass and the metallicity of the hosting stellar population. In addition, a long-standing puzzle has been the role of Helium white dwarfs as accreting objects in mass-transferring binaries. Initial indications are that the masses needed for unstable Hydrogen-burning flashes will be very large on these cold, low gravity objects, potentially providing the ideal environment for outbursts like that seen in M31 as the ''red variable''.It is expected that this work will motivate new transient surveys of distant galaxies. Moreover, the graduate students involved in the project will be trained in theory, numerical modeling, and data acquisition. The PI will continue to accelerate the inclusion of the Las Cumbres Observatory Global Telescope Network into the international astrophysics community. The development of a K-12 astronomy curriculum for local outreach Docents will enhance their efforts, especially amongst under-represented minorities.