Prospects for Refining Kepler TTV Masses Using TESS Observations

Abstract

In this paper we investigate systems previously identified to exhibit transit timing variations (TTVs) in Kepler data, with the goal of predicting the expected improvements to the mass and eccentricity constraints that will arise from combining Kepler data with future data from the TESS mission. We advocate for the use of the Kullback-Leibler (KL) divergence as a means to quantify improvements in the measured constraints. Compared to the original Kepler data, the TESS data will have a lower signal-tonoise ratio, rendering some of the planetary transits undetectable, and lowering the accuracy with which the transit mid-time can be estimated. Despite these difficulties, out of the 55 systems (containing 143 planets) investigated, we predict that the collection of short-cadence data by TESS will be of significant value (i.e. it will improve the mass uncertainty such that the KL divergence is > ∼ 0.1) for approximately 6 -14 planets during the nominal mission, with the range primarily driven by the uncertain precision with which transit mid-times will be recovered from TESS data. In an extended mission this would increase to a total of approximately 12 -25 planets.

Science Extraction from TESS Observations of Known Exoplanet Hosts

“…Some of the most exciting science from Kepler came from systems of multiple transiting planets, particularly those where planet-planet interactions revealed by Transit Timing Variations (TTVs) provided an important source of mass measurements and constraints (e.g., Steffen et al 2013;Hadden & Lithwick 2014). Such observations of TTVs are also true for TESS but to a more limited extent (Goldberg et al 2019;Hadden et al 2019). Kane et al (2019) investigated the degradation of TTV signals when switching from Kepler's 4-year duration to the 6-12 month duration of TESS.…”

Prospects for TTV Detection and Dynamical Constraints with TESS

“…We use Equation (1) to estimate the expected transit mid-time uncertainty, σ tc , for each planet in our sample, by combining the photometric uncertainty, σ, of the host star with the transit depth, duration, and ingress times computed from the planet's radius and orbital properties. Goldberg et al (2019) demonstrate that Equation (1) accurately predicts the preci-…”

“…For example, Rodriguez et al (2018) constrain two planetary masses using just nine TTV data points that cover a single planet-planet conjunction. Furthermore, Goldberg et al (2019) show that it will be possible to combine TESS's short time baseline observations with previous Kepler observations to refine dynamical constraints for a handful of TTV systems.…”

Revisiting the Kepler field with TESS: Improved ephemerides using TESS 2min data

“…The updated systems in this work included a number of Kepler multi-planet systems known to exhibit significant TTVs, namely Kepler-18, Kepler-25, Kepler-51, Kepler-89, and Kepler-396 (Cochran et al 2011;Steffen et al 2012Steffen et al , 2013Masuda 2014;Weiss et al 2013;Xie 2014). Most of these systems were independently highlighted as worthwhile systems for further TTV analysis by Goldberg et al (2018) and/or Jontof-Hutter et al (2021). In an attempt to update the TTV masses for planets in these systems, additional TTV fitting was carried out.…”

“…They also suggest that TESS may be very powerful for investigating longer-term transit timing variations. These thoughts are echoed by the modelling of Goldberg et al (2018) where they conclude that mass uncertainties could be improved for 6-14 planets with the new TESS 2min data, depending on the eventual measurement uncertainties.…”