Some Effects of Magnetic Intensification on Stellar RVs

Magnetic intensification (MI) acts to change the shape and strength of lines in a magnetic field. Magnetic regions rotating across stellar disks will thus produce traveling deformations in absorption line profiles that will cause apparent radial velocity (RV) shifts. The size of the MI effect depends on the line's Lande geff value, number and relative strength of the Zeeman components, field strength, line strength, and wavelength. I compute simple magnetic radiative transfer models and rotate lines with various geff and Zeeman patterns across model stellar disks to estimate the effect on stellar RVs. I find that for the simplest case, that of a simple triplet, the effect is significant at the ±13 m/s level for a plage covering 1% of a Sun-like star and a modified HARPS RV line list. The magnitude of the MI effect can increase with more complex Zeeman patterns. MI thus poses a significant challenge for sub m/s RV work; its complex dependences argue for a line-by-line approach to RV analyses.