Figure reproduced from Roettenbacher et al. 2011 (KIC 2438502)
Figures reproduced from Roettenbacher et al. 2015 (o Dra)
The high-precision, nearly-uninterrupted photometry of the Kepler satellite allows for the detection of Earth-sized planets around Sun-like stars. In addition to planet discovery, these data lend themselves well to tracking the quickly-changing starspots of rapidly-rotating stars (see figure, below).
Using a light-curve inversion algorithm, I create stellar surfaces from the Kepler light curves. These surfaces represent single rotation periods, and studying many sequential surfaces allows for investigations of differential rotation, spot longevity, and activity cycles.
In addition to starspots, these rapidly-rotating stars exhibit strong flaring activity. I investigate the presence of activity cycles in the timing and strength of the observed flares.
Recently, I have been investigating the effect of starspots on the eclipse depth of a close binary system. The results of this study can be applied not only to Kepler light curves but also to light curves from future missions, such as TESS.
STARSPOT EVOLUTION, FLARES, AND TRANSITS
Using three state-of-the-art imaging techniques, I image the spotted surfaces of the giant primary stars of RS CVn binary systems. These cool giants have strong magnetic fields, which have a tendency to form large starspots.
I compare sub-milliarcsecond resolution interferometry, high-resolution spectroscopy, and ground-based photometry to create a contemporaneous set of aperture synthesis, Doppler, and light-curve inversion images, respectively. With these data, I identify the benefits and the drawbacks of each of the different techniques while comparing their results.
Additionally, with the images illustrating the stellar surfaces at a single point in time, I investigate the existence of polar starspots. These unique starspots have only been observed with Doppler imaging, and remain unverified by another imaging method.
While imaging RS CVn systems, I have been able to constrain orbital parameters by making the first visual detections of the companions and combining with the first double-lined spectroscopic orbits, (see figure, right, top). With the orbit, masses of the components can be calculated. With the system parameters determined, I model the light curve and have made the first detections of ellipsoidal variations of the primary stars (see figure right, bottom).
With the positive identification of ellipsoidal variations, we are able to measure gravity darkening in stars with convective envelopes.