Multiwavelength and Multidimensional Studies of the Nova Outburst and Related Objects

对新星爆炸的进一步了解对于银河系中许多化学元素的形成、近距离双星系统的长期演化、前太阳颗粒的来源、宇宙的距离尺度、Ia型超新星祖先的性质以及伽玛射线源都具有重要意义。在紧密的双星系统中，白矮星富氢包层中的热核逃逸构成了经典新星和复发新星的爆发机制。正在进行的对这些爆炸的一般特征的研究使我们了解了双星的演化，而对新星双星系统演化的研究则限制了Ia型超新星（未确定的）祖星的模型。此外，新星的峰值亮度和衰减速率之间的经验关系在理论上还不能被理解，这使得新星可以被用作标准烛光来确定远至某些星系团的距离。对新星喷出物的大量丰度测定表明，在一些系统中存在质量较大的氧-氖-镁白矮星，而在另一些系统中存在质量较小的碳-氧白矮星。新星喷出物中从碳到硫等元素的高度富集证实了从下面的白矮星的核心中有大量的物质被挖掘出来。因此，经典新星必须参与星际气体和尘埃中重元素的化学富集循环。一旦进入弥漫气体，这些物质就会在分子云中循环，然后在恒星形成过程中被合并到年轻的恒星和行星系统中。似乎来自新星的颗粒被注入到前太阳星云中，并且可以与陨石中发现的一些前太阳颗粒相识别。这项研究将帮助我们(1)理解和可靠地预测上述观察到的行为，以及(2)理解热核失控最后阶段核物理和对流之间复杂的相互作用。＊＊＊

AST 0206003PI StarrfieldAn improved understanding of nova explosions holds important implications for the creation of many chemical elements in the galaxy, the secular evolution of close binary systems, the sources of pre-solar grains, the distance scale of the universe, the nature of the progenitors of Type Ia Supernovae, and for gamma-ray sources. Thermonuclear runaways in hydrogen-rich envelopes on white dwarf stars in close binary stellar systems constitute the outburst mechanisms for classical and recurrent novae. Ongoing studies of the general characteristics of these explosions are informing us about binary stellar evolution, while studies of the evolution of nova binary systems are constraining models for the (unidentified) progenitors of the Type Ia supernovae. Further, the empirical relation between the peak luminosity of a nova and the rate of decline, not understood theoretically, allows novae to be utilized as standard candles for distance determinations as far away as some galaxy clusters. Extensive abundance determinations of nova ejecta have revealed the existence of massive oxygen-neon-magnesium white dwarfs in some systems and less massive carbon-oxygen white dwarfs in other systems. The high levels of enrichment of novae ejecta in elements ranging from carbon to sulfur confirm that there is significant dredge-up of matter from the core of the underlying white dwarf. Classical novae, therefore, must participate in the cycle of chemical enrichment of heavy elements in interstellar gas and dust. Once in the diffuse gas, this material is cycled through molecular clouds before being incorporated into young stars and planetary systems during star formation. It seems likely that grains from novae were injected into the pre-solar nebula and can be identified with some of the pre-solar grains found in meteorites. This research will help us (1) to understand and to reliably predict the observed behaviors described above, and (2) to understand the complicated interplay between nuclear physics and convection during the final stages of the thermonuclear runaway. ***