Mapping Matter in Strong Gravity: Spectral-Timing of Black Holes and Neutron Stars

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Abigail Stevens is awarded an NSF Astronomy and Astrophysics Fellowship to carry out a program of research and education at Michigan State University and at the University of Michigan. Stevens will study the X-rays emitted when black holes and neutron stars interact with low-mass stars, focusing on very rapid changes in emission called quasi-periodic oscillations (QPOs). Stevens will study how the energy spectrum and timing of X-rays changes during QPOs. This is a probe of how matter behaves close to black holes and neutron stars, and it will help astronomers to better understand the strong gravitational and magnetic fields found nowhere else in nature. Alongside her research, Stevens will establish a middle school outreach program in the Lansing Public School District. There she will develop and lead activity-based interactive astronomy lessons on the topics of the Sun, the Solar System, and supermassive black holes and galaxies.Stevens will use phase-resolved spectroscopy of different types of QPOs and pulsations in low-mass X-ray binaries (LXMBs), which contain a compact object, a low-mass stellar companion, and an accretion disk of stellar material around the compact object. She will use a spectral-timing technique developed during her PhD thesis, as well as comprehensive physical models, to compare the geometry of the emitting region in black holes with that in neutron stars and determine the changing inner configuration of LMXBs in the strong-gravity regime. This work will lead to better understanding of intense gravitational fields, viscous astrophysical plasmas, and very strong magnetic fields. Stevens will also work with outreach facilities at her host universities to conduct astronomy enrichment in local area middle school classes. 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.