Multiwavelength and Multidimensional Studies of the Nova Outburst and Related Objects

Arizona State University, Scottsdale AZ

Investigators

Abstract

AST 0206003 PI Starrfield An 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. ***