The work to be carried out under this award will develop the needed infrastructure and apply it to study realistic compact binary systems that can give rise to gamma ray burst phenomena. To this end the required physics modules will be incorporated in a new infrastructure framework able to exploit the new generation of high performance computers. The implementations of this infrastructure will allow study of the system in depth, with the goal of predicting and interpreting aspects of observations of electromagnetic and gravitational waves.
This work serves to advance computational and numerical techniques for an exciting scientific problem, as well as the creation and dissemination of advanced tools for distributed computing. The research to be carried out has as its goal to give an unprecedented description of possible (short) gamma ray burst systems and to develop a new computational model to efficiently utilize petascale computing. Finally, this study involves the training of postdoctoral researchers, graduate students, and undergraduates.
We have examined the dynamics associated with various astrophysical systems incorporating with strong-field gravity. Using a distributed adaptive mesh refinement code capable of solving the fully nonlinear Einstein equations coupled to a fluid obeying the MHD approximation, we carried out a number of numerical evolutions. We found that gravitational signatures from compact binaries could reveal information about the magnetic field of the stars based on a comparison of a run with unmagnetized neutron stars and a run with magnetized stars. We have studied the mixed binary case consisting of a black hole and a neutron star both with no initial magnetization and with magnetization. We have also studied binary black hole merger within the force free approximation and found collimated Poynting flux associated with each individual black hole. We have continued this line of research by studying the Poynting flux associated with spinning black holes. When a black is both moving (translational momentum) and spinning (angular momentum) with respect to an ambient magnetic field, we find a generalized Blandford-Znajek effect in which the kinetic energy of the black hole is converted to electromagnetic energy. Such emission should have observational consequences which may enable concurrent detection of such events in GW and EM bands. The project has aided in the instruction of graduate students such as Michael Besselman (@BYU) and Miguel Megevand (@LSU), and also the training of postdoc Carlos Palenzuela (then @LSU). The project has resulted in a number of publications and conference talks.
