The Project

EXOplanetary dynamics and stability: Reverse Engineering of STable multi-planet ARchitecTures (EXO-RESTART)

The project aims to homogeneously re-analyze the observed statistical and physical characteristics of all literature, and newly discovered multi-planet systems. The immediate objective is to perform the first homogeneous dynamical modeling of high-precision Doppler (RV) and transit photometry data consistent with multiple-planet systems and apply extensive long-term stability analysis to reveal the current dynamical architecture. The ultimate goal of EXO-RESTART is to conduct planet migration and planet-planet scattering simulations to probe the formation mechanisms of high-order mean motion resonance (MMR) systems, eccentric multiple-planet systems, and circumprimary planets in close binary systems, which are currently poorly studied. These analyses will reveal the primordial planet-disk conditions needed to assemble the observed planetary architectures.

OBJECTIVES

Full homogeneous re-analysis of archival RVs

We aim to perform a complete homogeneous re-analysis of archival RV surveys, such as HARPS, HIRES, FEROS, and CARMENES,  which cover more than 6000 unique stars. We rely on the Exo-Striker exoplanet toolbox (Trifonov, 2019), which is currently under development, especially for the needs of the EXO-RESTART project.

We have developed a semi-automated Exo-Striker pipeline, combining RVs, transit data, searching for planets, and performing the orbital analysis for each target. The Exo-Striker is open-source software and is available here.

Detailed analysis of multiple-planet systems

The figure shows an N-body fit of a multiple-planet system discovered with Doppler surveys (Antonova et al., in prep). Many archival, unpublished RVs are available for such systems. An immediate objective of EXO-RESTART is to perform the first homogeneous dynamical modeling of high-precision Doppler and transit photometry data consistent with multiple-planet systems to reveal the current dynamical architecture.

 

 

We also aim to dynamically characterize TESS/Kepler TTVs multiple-planet systems like the TOI-2525 system (Trifonov et al. submitted) shown below.

 

Long-term stability and resonance analysis of multiple-planet systems

The figure shows a clear 2:1 eccentricity-type MMR systems recovered by applying an N-body model to RV data. In EXO-RESTART we will invest efforts in understanding the dynamical architecture and long-term stability of the newly revisited multiple-planet systems. We will especially focus on MMR pairs like the one shown below.

 

 

TESS follow-up & exoplanet characterization

The figure shows the TESS transit+RV fitting results of the nearby Super-earth discovery of Gl486b (Trifonov et al., 2021b, Caballero et al. 2022). Gl486b is a prime target for atmospheric characterization with the JWST. TESS is already uncovering hundreds of transiting exoplanet candidates around nearby stars, such as Gl486b. Many of them are members of multiple-planet systems, which we aim to characterize. Our team has ample experience with TESS light curves. We aim to analyze public TESS data jointly with archival and new RV data. Multiple planet systems will be modeled with self-consistent transit and RV models, which take into account the gravitational interaction between the planets. These superior models will be used for a more detailed dynamical analysis of near-resonant chains of transiting planets.

 

Resonance capture simulations

The figure shows resonance capture simulation at the 2:1 MMR in an anti-aligned configuration. One of the ultimate goals of EXO-RESTART is to conduct planet migration and planet-planet scattering simulations to probe the formation mechanisms of low-order MMR systems, and near-resonant multiple-planet systems. These analyses will reveal the primordial planet-disk conditions needed to assemble the observed planetary architectures.

Formation of high-order MMR

The figure shows multiple-planet systems discovered via the Doppler method and orbiting stars with estimated masses larger than 1.3 Msol. The left panel shows the published best-fit period ratio for the planetary systems. The right panel shows the planetary semi-major axes. The blue dashed line is the protoplanetary phase ice-line radius. We aim to conduct planet migration and planet-planet scattering simulations to probe the formation mechanisms of high-order MMR systems, eccentric multiple-planet systems, and circumprimary planets in close binary systems, which are currently poorly studied. These analyses will reveal the primordial planet-disk conditions needed to assemble the observed planetary architectures.

 

Acknowledgements:

This work is supported by the “EXO-RESTART” project, funded under the Bulgarian National Science Fund program “VIHREN-2021” project No. KP-06-DV/5.