Mass Upper Bounds for Over 50 Kepler Planets Using Low-S/N Transit Timing Variations

TL;DR

This paper introduces a method to estimate upper bounds on the masses of Kepler planets using low-S/N transit timing variations, expanding mass measurements for dimmer systems where traditional methods are challenging.

Contribution

The authors develop a novel approach to constrain planet masses with low-S/N TTVs, enabling mass estimates for a larger fraction of Kepler planets.

Findings

Over 30% of analyzed planets have informative mass upper bounds from low-S/N TTVs.

Low-S/N TTVs suggest some small planets are volatile-rich.

Mass constraints from TTVs are consistent with RV measurements where available.

Abstract

Prospects for expanding the available mass measurements of the Kepler sample are limited. Planet masses have typically been inferred via radial velocity (RV) measurements of the host star or time-series modeling of transit timing variations (TTVs) in multiplanet systems; however, the majority of Kepler hosts are too dim for RV follow-up, and only a select number of systems have strong enough TTVs for time-series modeling. Here, we develop a method of constraining planet mass in multiplanet systems using low signal-to-noise ratio (S/N) TTVs. For a sample of 175 planets in 79 multiplanet systems from the California-Kepler Survey, we infer posteriors on planet mass using publicly available TTV time-series from Kepler. For 53 planets ($>30\%$ of our sample), low-S/N TTVs yield informative upper bounds on planet mass, i.e., the mass constraint strongly deviates from the prior on mass and yields a physically reasonable bulk composition. For 25 small planets, low-S/N TTVs favor volatile-rich compositions. Where available, low-S/N TTV-based mass constraints are consistent with RV-derived masses. TTV time-series are publicly available for each Kepler planet, and the compactness of Kepler systems makes TTV-based constraints informative for a substantial fraction of multiplanet systems. Leveraging low-S/N TTVs offers a valuable path toward increasing the available mass constraints of the Kepler sample.