My research focus is in observational stellar astronomy. 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. Surprisingly little is known about how the basic properties of these stars evolve after they reach an age of a few hundred million years -- at which point they are still toddlers, since very low-mass stars can live tens of billions of years, and even the (relatively massive) Sun will live about ten billion years! I am therefore measuring and comparing stellar rotation and magnetic activity in a number of stellar clusters of different ages. These clusters have homogeneous, single-aged populations that are the key for calibrating the relationship between stellar age, rotation, and activity.
I also 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. In particular, I am interested in observationally constraining the mass-radius relationship for neutron stars, and in uncovering the expected (but unseen) companions to recently discovered low-mass white dwarfs (which have masses less than 20% that of the Sun).
In exploring these topics, I make observations at wavelengths ranging from X-rays to the infrared. I also use large-scale survey data, both photometric and spectroscopic.