Habitable Zone Super-Earths with Non-Stabilised Spectrographs

Detecting the small velocity amplitudes (<= 10 m/s) produced by habitable zone rocky planets around M Dwarfs requires radial velocity precisions of a few m s^-1. However, an iodine absorption cell, commonly used as a high precision wavelength reference on non-stabilised spectrographs, is not efficient for very red and faint objects like M Dwarfs. Instead, arc lamps have to be used. With the exception of the ultra-stabilised HARPS spectrograph, achieving ~m s^-1 calibration with arc lamps has not been possible because typical spectrographs experience drifts of several hundred m s^-1 due to local atmospheric changes in pressure and temperature. We outline and present results from an innovative differential wavelength calibration method that enables ~m s^-1 precision from non-stabilised, high-resolution spectrographs. This technique allows the detection of rocky planets with radial velocity amplitudes of a few m s^-1.