Spectropolarimetry in optical and near-IR for EV Lac and AD Leo: what is stellar activity's favourite colour?

Stellar activity hinders the detection of small exoplanets with the radial velocity (RV) method, because it introduces spurious signals that can drown or mimic planetary signatures. It is therefore crucial to understand and filter out activity signals, especially in light of future small planet searches.

We investigate ways to reduce activity jitter in RV time series using spectropolarimetric data sets in optical (ESPaDOnS@CHFT and NARVAL@TBL), and in near-infrared (nIR) with SPIRou@CHFT. We employ two approaches: 1) perform a chromatic study of typical stellar activity proxies, and  2) study a parametric selection of spectral lines to build a mask for Least-Square Deconvolution. The study is performed for EV Lac and AD Leo, two very active M dwarfs.