Research

The Automated Planet Finder (APF) is a 2.4 meter telescope located at Lick Observatory atop Mt. Hamilton in northern California. The telescope and its accompanying high resolution echelle spectrograph were specifically designed to detect planets in the liquid water habitable zone of low mass stars. The telescope is operated every night (weather permitting) to help achieve meaningful signal-to-noise gains from high cadence observing. A technical overview of the telescope, dome and the optical train, including the Levy echelle, can be found in Vogt et al. 2014. The spectrograph's resolving power (R~100,000 for RV observations) means that the APF is especially effective when observing M dwarfs, with their high density of absorption lines. Indeed, the APF achieves the same speed-on-sky (precision/exposure time) as the HIRES instrument on Keck-I when observing M dwarfs.

Long term, high cadence monitoring, however, is not ideal for human observers. Working with APF through a full range of conditions and contingencies, I learned the intricacies of the telescope and the spectrograph and determined which factors have the greatest effect on observing efficiency and precision. I took my three years of observing experience and turned them into the design of the dynamic scheduler that now runs the telescope every night. The scheduler makes informed target selections on a minute-to-minute basis, based on my team's science goals and current atmospheric conditions  as described in Burt et al. 2015. In addition to producing world-class radial velocities, the spectra extracted from every APF observation contain the Ca II H & K and Hα lines, used we use to assess chromospheric activity.

I focus on later type stars, specifically K and M dwarfs. I am especially intersted in host stars that show evidence of both inner planets, which have a better chance of transiting and providing a radius estimate, and long period planets which set interesting constraints on the formation and evolution of the system.

I am fortunate to observe both with the APF and with the Planet Finder Spectrograph on the Magellan telescopes located above La Serena, Chile. My various teammates and I have contributed to a number of planet discovery papers, including finding a 6 planet system around one of the closest stars (Vogt+, 2015). More recently, we are starting to focus on obtaining mass measurements for planets detected with the K2 mission in order to add more points to the mass:radius diagram and improve the community's understanding of the composition of super-Earth planets.

The next big project for the APF will be providing RV observations in support of NASA's Transiting Exoplanet Survey Satellite (TESS) which is set to launch in early 2018 and use transit photometry to look for evidence of planets around the closest, brightest stars.

Thanks to its focus on bright stars and the location of its overlap zone near the North ecliptic pole (of which the APF, located in San Jose, CA, has year-round visibility), TESS’s stars will make optimal targets for the APF. I'm currently designing a new and improved dynamic scheduler with time varying priorities in anticipation of the TESS results. The new format will balance observing a non-trivial number of TESS stars in the overlap zone and making sure that each star is observed for long enough each night and often enough each month to provide real constraints on the masses of any planets TESS detects. Additionally, I'm surveying the brightest stars in the NEP to get an idea of which ones are quiet enough from an RV point of view to give us a chance at detecting small planetray signals.