Collaborative Research: Asymmetry is Destiny: Structure and Fate of Wolf-Rayet Binary Systems

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Supernovae are the most energetic explosions known. The very most energetic supernovae (SNe) are thought to form from the direct collapse of a rapidly rotating star into a black hole. The types of stellar systems which produce these SNe are not well understood. The very hot, massive stars known as Wolf-Rayet (WR) stars are capable of producing features observed in such SNe explosions. However, the role of WR stars in binary star systems in producing supernovae has not been observationally studied in detail. The investigators will use large telescopes to show how the light from such SNe explosions is polarized; this will help determine how the explosion occurred. They will then use computer models to better understand and interpret material flowing out from the supernovae. They will organize a summer camp for middle-school girls of color, following up with mentoring throughout the school year. They will then assess the feasibility of establishing such a program at USNA. This project uses the method of spectropolarimetry to observationally determine the morphology of the winds in WR binaries. Spectropolarimetry probes the scattering history of polarized emission lines, revealing their formation and scattering locations within the system. Existing polarimetric observations of the V444 Cyg system, a prototypical WR+O eclipsing binary, suggest that a shock-cone structure exists due to the collision of the two stars' winds. The study will quantify this behavior in similar systems and determine the range of morphological characteristics winds in WR+O display. Monte Carlo modeling will allow the team to interpret the results, predict polarimetric signatures from interacting binary stars, and compare the results to current theories of WR winds and binary evolutions. They propose to continue a successful pilot project using the RRS instrument on the South African Large Telescope to construct well-sampled polarization phase curves for ~15 WR binary systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.