Searching for Planets around Red Stars: New Calibrations and Detections

Sara Gettel, CfA

I present results from projects focusing on planet detection around two classes of red stars. For the first project, the absorption cell technique for calibrating radial velocities is modified to use the telluric bands found between ~6000-9000 A. These features are stable to < 10 m s-1 and access the increased red flux of low-mass and evolved stars. I carry out a mock survey around RV stable early M dwarfs. Radial velocities are measured for a small number of blocks and compared to analogous measurements made using iodine calibration, yielding a precision of ~20 m s-1 with iodine calibration and ~30 ms-1 with telluric calibration. Both of these results may be improved with further work, nevertheless it is reassuring to obtain similar results with the two calibration methods. With the present level of precision, telluric calibration would be able to detect a Neptune-mass planet in the habitable zone of an M dwarf.

The second project is part of a search for substellar companions to K giants. Results include the discovery of planetary systems around five evolved stars that illustrate the differences between planet detection around giants and Solar-type stars, including increased masses and a lack of short period planets. I describe the unique features of these systems, including binary companions, very long period orbits and the increased RV 'jitter' typical of giant stars. I also show that, if the jitter is caused by p-mode oscillations, the amplitude of this noise is anti-correlated with metallicity.