Exoplanets & Stellar Populations Group

TRADES project

Borsato et al. (2014) A&A, 571, 38

Our group is developing TRADES (TRAnsits and Dynamics of Exoplanetary Systems), a FORTRAN code (parallelized with openMP) that simulates an N-body system in order to analyze the dynamics of an exoplanetary system.
It is possible to characterize a planetary system combining the results of different techniques, such as radial velocities (RV), transit times (T₀), and Transit Times Variation (TTV); nevertheless this is a difficult inverse problem. To solve this problem, in TRADES has been implemented the direct N-body approach, that is simpler than the analytical one based on perturbation theory, but it is more computationally intensive.
During the orbital integration, TRADES calculates the T₀ and the RVs and compares them with the observations allowing the modelling of the dynamics of multiple planet systems. Our group implemented different algorithms to probe the huge space of parameters. TRADES can search a quasi-global orbital solution with a grid search (it varies the period, eccentricity, and argument of pericenter of one of the bodies), with a genetic algorithm (PIKAIA), or with a particle swarm optimization (PSO), while it can determine the local solution with the Levenberg-Marquardt (LM) algorithm.
TRADES calculates the parameter errors from the LM as the square root of the diagonal elements of the covariance matrix and it can calculate the confidence intervals of the parameters with a bootstrap analysis.
This tool is ready to fit, also, the duration of the transits in order to put more constraints on the orbital parameters. Furthermore, we are planning to implement a Bayesian algorithm, such as a Monte-Carlo-Markov-Chain (MCMC), and to add a tool for the analysis of the dynamical stability of the orbtital solution.
For more information about the project and all TRADES papers, please contact Luca Borsato.

Related papers to TRADES project:

• Borsato et al. (2014) A&A, 571, 38

The Fortran90 code, with an user guide are now avaliable: TRADES by Luca Borsato - 2016 on .