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