IA/U.Porto Seminar - Detecting Exoplanets with Compressed Sensing Techniques - 15 fevereiro 2017

When a star has planetary companions, it describes an epicyclic motion around the center of mass of the system. The component of the star velocity in the observer's direction is visible in spectroscopic measurements thanks to Doppler effect. In the radial velocity time series, one searches for periodic variations due to planets. Various phenomena complicate the task: the signals from several planets can be hard to disentangle, stellar noise might mimic planetary signals, correlated noise buries other signals etc. Most recent approaches privilege fitting a complete model instead of fitting planets one by one, since global searches reduce both rates of false positives and false negatives. Unfortunately, the performance improvement comes at the cost of a greater computational complexity.

 

We will present a method based on Compressed Sensing that allows to search for several planets at once but without random searches, which makes the algorithm faster than MCMC and genetic algorithms. The tool can be used as a Lomb-Scargle periodogram but has two advantages: it avoids most cases where the tallest peak of the periodogram is spurious. Secondly, one can see on a single graph the various orbital periods and in some cases the frequencies due to the gravitational interactions between planets.