My research spans a wide range of interests including the co-evolution of galaxies and supermassive black holes, the evolution of AGN activity and X-ray binaries over cosmic history, and detailed studies of X-ray sources in the Milky Way and nearby galaxies.  I use observations from X-ray satellites, including Chandra, NuSTAR, and XMM-Newton, to study X-ray sources in the Milky Way and external galaxies.

Thesis Topic: High-Mass X-ray Binaries

Artist's impression of Cygnus X-1, a Galactic HMXB harboring a black hole.

Artist’s impression of Cygnus X-1, a Galactic HMXB harboring a black hole.

My graduate research is focused on high-mass X-ray binaries (HMXBs), binary systems consisting of a neutron star (NS) or black hole (BH) accreting mass from a massive stellar companion.  In the majority of Galactic HMXBs, the compact object accretes matter directly from the stellar wind of the companion, while in a small number, accretion occurs through Roche-lobe overflow of the companion.  HMXBs allow us to study the physics of accretion onto compact objects and the stellar winds of massive stars; they can inform our understanding of the evolution of massive stars and our estimates of the number of NS+NS, NS+BH, or BH+BH binaries that are likely to merge and produce gravitational waves that could be detected by experiments such as Advanced-LIGO.  Although these systems are relatively rare, they are nonetheless relevant to galaxy evolution: HMXBs ca be useful star-formation indicators in external galaxies, could make a significant contribution to the ionizing flux during the Epoch of Reionization, and may be important sources of feedback in low-mass galaxies.

The goal of my thesis work is to improve our understanding of the evolution of HMXBs by identifying and studying the quiescent HMXB population, constraining the fraction of HMXBs that host a BH, and comparing HMXB populations in different galaxy environments.


John Tomsick, Space Sciences Laboratory, UC Berkeley

Mariska Kriek, Astronomy Department, UC Berkeley