Research Overview

Neutron stars are fascinating objects. They are formed within a supernova explosion by the intense pressure of a star’s mass collapsing in on itself. Stabilized by neutron degeneracy pressure, a neutron star contains the mass of almost twice the Sun within an approximately 13 mile diameter. The material of a neutron star is incredibly dense and magnetic. Neutron stars host the Universe’s most powerful magnetic fields, which can be trillions of times stronger than Earth’s magnetic field. Neutron stars also have strong gravitational fields but, luckily for those of us who study these objects, the gravitational field of a neutron star is weaker than that of a black hole, which means that it is possible for us to observe the neutron star surface and the extreme environment surrounding it.

My research focuses on accreting neutron star X-ray binaries. This type of system is formed when a a neutron star closely orbits a regular star. Some of the regular star’s outer layers will shed gas, which can become gravitationally trapped by the neutron star and fall towards it, forming an in-spiraling disk of gas called an accretion disk. The gas will become denser and hotter as it falls towards the neutron star under the influence of gravity. However, at the edge of the neutron star’s magnetic field, the magnetic forces dominate the force of gravity and cause the hot gas to travel along magnetic field lines, effectively funneling gas in arching streams and dumping it onto the magnetic poles of the neutron star. The shape, structure, and behavior of these streams with time can tell us about the magnetic properties of neutron stars and the fundamental physics of how particles interact with powerful magnetic fields. Studying magnetic accretion is not only important in accreting X-ray binaries – it is also relevant for accretion onto supermassive black holes, young stars, and white dwarfs.

My research has led me to study objects with warped accretion disks where we can more easily determine the shape and behavior of the accretion disk. I have used X-ray spectroscopy and X-ray timing analyses to simulate warped disk geometry and track changes in unstable accretion disks. For more detail about my research, please see my publication list below.

I look forward to expanding my research at Middlebury and including undergraduate student in my research program. If you are a Middlebury student interested in working with me, please send me an email at mbrumback (at) middlebury.edu.

Publication List

For a full list of my first author and contributing author publications, please read my linked ADS library.