Facility for Rare Isotope Beams

The cosmic stellar birth rate can be measured by standard astronomical techniques. It can also be probed via the cosmic stellar death rate, though until recently, this was much less precise. However, recent results based on measured supernova rates, and importantly, also on the attendant diffuse fluxes of neutrinos and gamma rays, have become competitive, and a concordant history of stellar birth and death is emerging. These new probes of the star formation history will also provide unique constraints on the physics of core-collapse and type Ia supernovae.

Women made a host of contributions to the Manhattan Project, the United States’ massive 1940s effort to build an atomic bomb. Yet for most of the second half of the 20th century, descriptions of such contributions were limited to accounts of women lending their support as clerks, truck drivers, and dutiful spouses. That changed in 1999 with the publication of Their Day in the Sun: Women of the Manhattan Project, co-authored by Ruth Howes, professor and chair of the Physics Department at Marquette University. In an open public lecture, Howes will highlight and extend some of the main themes from her book, notably, that women employed as physicists, chemists, mathematicians, life scientists, and technicians were critical to the success of the project that helped end World War II.

Binary mergers involving black holes and neutron stars have been proposed as major sources of gravitational waves, r--process nucleosynthesis, and short gamma-ray bursters. In addition, they represent an important, and possibly unique, observable that could distinguish between normal and self--bound neutron stars. These two families of stars have distinctly different mass--radius relationships resulting from their equations of state which can be revealed during their mergers if stable mass transfer ensues. The two cases of gravitational-radiation induced binary mergers: (i) a black hole and a normal neutron star, and (ii) a black hole and a self-bound strange quark matter star will be highlighted. Analysis shows that differences in the evolution of normal neutron stars and strange quark matter stars are significant and could be detected in gravity waves. Both the amplitude and frequencies of the wave pattern are affected. In addition, details of the equation of state for either normal neutron stars or strange quark stars may be learned.

The five year Supernova Legacy Survey (SNLS) has discovered more than 350 Type Ia supernovae (SNe Ia) in four years of operation with the goal of measuring the Dark Energy equation of state, w. In addition to producing the best published constraints on Dark Energy, we have made progress in understanding Type Ia supernovae as distance indicators and astrophysical phenomena. One surprise is the case of SNLS-03D3bb, a supernova whose extreme brightness and low expansion velocity imply that it is the explosion of a white dwarf that exceeded the theoretical maximum mass, the Chandrasekhar limit. This supernova is an extreme case of bright SNe Ia that are associated with star formation, whose rates are increasing with redshift. We show that the average properties of supernovae are evolving with redshift, and discuss the implications for current measurements of w and future measurements of time-variable w.

Among The Stars: The Life of Maria Mitchell Maria Mitchell sent a startling signal through the male-dominated world of science in the 19th century when she emerged as a world-class astronomer. In her 2007 book, critically acclaimed author Margaret Moore Booker describes Mitchell’s life and the stereotypes she struggled to change.

Stellar evolution is currently an exercise in spherical symmetry. The hydrodynamic processes taking place in stars, however, do not share this symmetry. Simplified models of the underlying hydrodynamics have been formulated, and have been quite successful in explaining the gross properties of stars. These models fail, however, when confronted with the ever more stringent observational tests that are becoming available. These failures have given birth to simplistic prescriptions for additional mixing at the boundaries of convection zones dubbed "overshoot" and "penetration". These obfuscating notions need to be replaced with an underlying physical picture. A powerful approach for investigating the complex flow present in stellar interiors is multi-dimensional hydrodynamic simulation. In this talk I will present an overview of the multi-dimensional simulations that we have been performing in the context of pre-supernova models and discuss how we are incorporating our new understanding into 1D stellar evolution codes.

In an attempt to constrain the astrophysical conditions for the nucleosynthesis of the classical r-process elements beyond Fe, we have performed large scale dynamical network calculations within the model of an adiabatically-expanding, high-entropy wind (HEW) of type II supernovae (SN II). A superposition of several entropy components (S) with model inherent weightings results in an excellent reproduction of the overall Solar system (SS) isotopic r-process residuals (Nr,⊙), as well as the more recent observations of elemental abundances of metal-poor, r-process rich halo-stars in the early Galaxy. For the heavy r-process elements beyond Sn, our HEW model predicts a robust abundance pattern up to the Th, U r-chronometer region. For the lighter neutron capture region, an S dependent superposition of (i) a normal component directly producing stable nuclei, including s-only isotopes, and (ii) a component from a neutron rich freezeout followed by the rapid recapture of beta delayed neutrons emitted from the far unstable seed nuclei is indicated.