Artistic representation of an planetary system around a star with an intense levels of magnetic activity
Credits: NASA, ESA, and G. Bacon (STScI)

Mario Damasso

Author: Mario Damasso Post-doc at INAF-OATo

Nowadays, the main obstacle to the detection of rocky planets with the radial velocity method isrepresented by stellar activity. The effects induced by the magnetic activity of a star can introduce signals of few m/s of amplitude into the data, that can be confused with those due to the dynamical interaction between the star and a low-mass planet.
The same activity-induced signals can prevent the detection of a planetary signal even when the existence of the planet is known, for instance thorough the photometric transit method, making a precise and significant measurement of the planetary mass a challenging task. The level of stellar activity is thus a key factor to take into account when planning spectroscopic observations aimed to detect small-amplitude planetary signals.

The statistical study by Damasso et al. published on MNRAS used a large number of injection/retrieval simulations to quantify how significantly low-amplitude planetary signals (1 m/s) injected in radial velocity time series are recovered, when the data are affected by quasi-periodic correlated noise due to stellar activity.
The simulations are devised taking into account some of the most performing high-resolution spectrographs presently used for exoplanetary science, as HARPS, HARPS-N, and HIRES, and are related to stars with different levels and properties of themagnetic activity.

The article “Biases in retrieving planetary signals in the presence of quasi-periodic stellar activity”is available here: