Computer Science – Performance
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21925001s&link_type=abstract
American Astronomical Society, AAS Meeting #219, #250.01
Computer Science
Performance
Scientific paper
R Coronae Borealis (RCB) stars have masses around a solar mass, are hydrogen-deficient variable stars that suddenly fade by several magnitudes at irregular intervals after which they gradually return to their original brightness over a period of some months. The fading is thought to be due to the formation of dust blocking light from the star. RCBs are often thought to be the result of the merger of a He and a CO white dwarfs. Here we present the results of 3 dimensional hydrodynamic simulations of the merger of double white dwarf systems where total mass is 0.9 solar mass and initial mass ratios ranging between q=0.5 and q=1. We use a zero-temperature plus ideal gas equation of state that allows for heating through shocks. These simulations allow us to follow the evolution of the system for 10-20 initial orbital periods (1000-2000 seconds) to a point after merger when the combined object has settled into a nearly steady-state like configuration. A hot shell forms around the merged core in low q simulations, but not in the high q simulations. The conditions found in the steady state like configuration is used as input to a nucleosynthesis code. We are particularly interested in seeing how much 18O is formed, as observations of RCB stars often show a very high ratio of 18O to 16O of order unity. In the very best case scenario, we find a ratio of 1/12 in the hot shell.
This work has been supported, in part, by grant OIA-0963375 from the U.S. National Science Foundation and, in part, by NASA/ATP grants NNX10AC72G. This research also has been made possible by grants of high-performance computing time on the TeraGrid (TG-AST090104), at LSU, and across LONI (Louisiana Optical Network Initiative), especially awards loni_astro08 and loni_astro09).
Clayton Geoffrey
Even Wesley
Fryer Chris L.
Geballe Theodore
Herwig Falk
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