My primary research area is brown dwarfs, objects with a mass below that required for stable hydrogen burning. I work with collaborators to identify candidate brown dwarfs in optical, near-infrared and mid-infrared sky surveys. We obtain optical through mid-infrared photometry and spectroscopy of these candidates, and brown dwarfs identified by other means, to compare to current model atmospheres. The goal is to determine the fundamental parameters of these faint, usually isolated, objects. If temperature and gravity can be determined then evolutionary models allow us to constrain both mass and age. As cooler and cooler brown dwarfs are found this work becomes more challenging observationally and theoretically.
A secondary research interest is cool white dwarfs. I have been involved with searches of sky surveys for low-temperature white dwarfs. The coolest white dwarfs, with effective temperature around 4000K, must be older than 8 Gyr, and so are useful for constraining the age of the Galaxy.