From Core to Outflow: The Dynamics of Binary Interactions and the Generation of Collimated Flows in Evolved Stars

University Of Rochester, Rochester NY

Investigators

Abstract

How stars are born and how they die represent the most fundamental kinds of questions we can ask about the Universe. For many years astronomers believed a star like our own sun would end its life by shedding it outer layers in a series of powerful winds leading to the formation of what is called a 'planetary nebula', a brightly glowing gas cloud that can span a light year or more. In this study the investigators explore how planetary nebula can form when stars are born with a sibling. More than half the stars in the sky live their entire life with a companion and that proximity can change the course of evolution for both stars. They seek to understand how two stars with about the same mass as the sun can interact at the end of their lives exchanging mass and driving winds that will create a planetary nebula. It may be that only binary stars form such nebula and our ideas of the Sun's eventual demise must be revised. Using powerful supercomputer simulations they will track the gas flows from the two orbiting stars and determine how these mass exchanges can alter the fate of the stars. These kinds of supercomputer algorithms are also used for other purposes, such as the high performance computer industry. This research project is focused on understanding magnetized outflows in evolved binary stars through specific new studies of Planetary Nebulae (PNe). As the final stage of mass loss for these stars, PNe represent a critical step in the mass and chemical evolution cycle for more than half the material ejected into the ISM. The ubiquity of PNe and their ease of observation also make them premier laboratories for testing new astrophysical theories. They will explore the dynamics of binary star mass transfer and mass loss through collimated outflows. The research will explicate routes through which accretion disks can form in evolved binary systems and attempt to provide limits on the accretion rates onto and through those disks. Using the conditions in the disks they will then study the formation and propagation of magnetic tower collimated outflows. These Poynting-Flux Dominated flows are of fundamental interest because they represent a different category of MHD outflow from the kinetic energy dominated flows that have received greater study. The binary evolution (Common Envelope), mass transfer and magnetic outflow processes they study are of fundamental importance to the study of many astrophysical systems from Type Ia SNe to Microquasars. In addition their work developing the AstroBEAR AMR code is of particular benefit computational astrophysicists Beyond the direct scientific research benefits of their study and the dissemination of the AstroBEAR software, the PI is a co-founder of National Pubic Radio's 13.7 Cosmos and Culture Blog, a regular on-air science commentator for NPR's All Things Considered and regular contributor to the New York Times. In this project they will develop a series of on-air programs for radio that will track the progress of a student and the post-doc as they carry out the research project.