# Kepler Planet Masses and Eccentricities from TTV Analysis

**Authors:** Sam Hadden, Yoram Lithwick  
**arXiv:** [1611.03516](https://arxiv.org/abs/1611.03516)  
**Date:** 2016-11-10  
**Summary page:** https://www.summarizepaper.com/en/paper/1611.03516v1/

## Key points

- Study analyzes transit timing variations (TTVs) of 145 planets from 55 Kepler multiplanet systems
- Objective is to infer planet masses and eccentricities, especially for 80 planets without previous measurements
- Two methods used: Markov chain Monte Carlo simulations and analytic fitting approach
- Mass measurements determined for 49 planets, including 12 previously uncharacterized ones
- Mass and radius measurements used to estimate gaseous envelopes surrounding the planets in TTV sample
- Analytic TTV formulae employed to overcome degeneracies in inferring eccentricities from TTV observations
- Planet eccentricities generally small but non-zero values suggest some orbits deviate from circularity
- Study expands understanding of planet masses and eccentricities within observed multiplanet systems by Kepler

## Summary

In their study titled "Kepler Planet Masses and Eccentricities from TTV Analysis," Sam Hadden and Yoram Lithwick conduct a comprehensive analysis of the transit timing variations (TTVs) of 145 planets from 55 Kepler multiplanet systems. The main objective of their research is to infer planet masses and eccentricities, particularly for the 80 planets that do not have previously reported measurements in these parameters. To achieve this, the authors employ two complementary methods to fit TTVs: Markov chain Monte Carlo simulations based on N-body integration and an analytic fitting approach. By applying these techniques, they are able to determine mass measurements for 49 planets, including 12 that had not been previously characterized. These mass measurements meet the authors' criterion for classification as robust. Additionally, Hadden and Lithwick use mass and radius measurements to estimate the masses of the gaseous envelopes surrounding the planets in their TTV sample, as well as transiting planets with radial velocity observations. This provides valuable insights into the composition and structure of these planetary atmospheres. The authors also leverage analytic TTV formulae to overcome degeneracies in inferring eccentricities from TTV observations. They find that while planet eccentricities are generally small - typically a few percent - there are instances where they are non-zero. This suggests that some planetary orbits deviate from perfect circularity. Overall, this study significantly expands our understanding of planet masses and eccentricities within multiplanet systems observed by Kepler. The combination of rigorous analysis techniques and insightful interpretations allows for more accurate characterizations of these exoplanets' physical properties.