My primary research interest is in observational stellar astronomy. Broadly speaking, I work on two different groups of objects. One is ordinary stars, typically less massive than the Sun, which are using the conversion of hydrogen into helium in their cores to prevent gravitational collapse. Many such stars have strong and active magnetic fields that are responsible for the production of X rays. However, the mechanisms underlying this emission -- and their relationship to fundamental stellar properties -- are not well understood. This is especially true in stars with masses below roughly 30% the mass of the Sun, which are fully convective and therefore lack the boundary between a radiative/convective zone needed to generate α-Ω dynamos such as that thought to power the Sun's magnetic field. Most recently, with Jenna Lemonias, I have been using the Palomar Transient Factory to obtain rotational periods for large numbers of X-ray emitting stars in nearby open clusters in an effort to explore the relation between rotation and activity at a variety of stellar ages.
In addition, I study white dwarfs and neutron stars, two of the possible endpoints of stellar evolution. In these stars fusion has ended and degeneracy pressure is preventing gravitational collapse. White dwarfs are typically the size of the Earth but 60% the mass of the Sun, while neutron stars, city-sized but roughly 1.4 times the mass of the Sun, are even more compact. I am working to place constraints on the neutron star equation of state, an area where observational astronomy intersects with theoretical physics. One major effort I am leading is to use catalog-level matching and follow-up observations to identify new candidate isolated neutron stars. These blackbody X-ray emitters may present the best opportunity to measure neutron star masses and radii under normal conditions (i.e., in the absence of significant accretion or strong magnetic fields); unfortunately only seven such objects are known.
I have also conducted multiwavelength observations of low-mass white dwarfs discovered in the Sloan Digital Sky Survey (SDSS). These white dwarfs have masses less than 20% that of the Sun, are thought to be the products of binary evolution, and are very likely to be paired with another compact object. However, there is no sign of companions to these white dwarfs in the SDSS data. My observations are intended to uncover these hidden companions; radial velocity monitoring in particular might allow us to measure the companion masses -- an exciting prospect if these unseen companions are in fact neutron stars. Most of these white dwarfs, however, appear to have other low-mass white dwarfs as companions, which is somewhat surprising. In light of this, I am currently working with Jeff Andrews to model the Galactic population of these white dwarf binaries.
For more details, you can read my research statement.