Doppler tomographic observations of exoplanetary transits

Transiting planet candidates around rapidly rotating stars, a number of which have been found by the Kepler mission, are not amenable to follow-up via the usual radial velocity techniques due to their rotationally broadened stellar lines. An alternative method is Doppler tomography. In this method, the distortions of the stellar spectral lines due to subtracted light during the transit are spectroscopically resolved. This allows us to not only validate the transiting planet candidate but also to obtain the spin-orbit misalignment for the system. The spin-orbit misalignment is a powerful statistical tracer of the migration histories of planets. I discuss our project to perform Doppler tomographic observations of Kepler candidates and other transiting planets using the facilities at McDonald Observatory. I present our first transit detection, that of Kepler-13 b, and discuss some other recent results.