Revisiting theKeplerfield withTESS: Improved ephemerides usingTESS2 min data

Matthew P Battley,David J Armstrong,Don Pollacco,Michelle Kunimoto

doi:10.1093/mnras/stab701

Abstract

ABSTRACTUp to date planet ephemerides are becoming increasingly important as exoplanet science moves from detecting exoplanets to characterizing their architectures and atmospheres in depth. In this work, ephemerides are updated for 22 Kepler planets and 4 Kepler planet candidates, constituting all Kepler planets and candidates with sufficient signal to noise in the TESS 2 min data set. A purely photometric method is utilized here to allow ephemeris updates for planets even when they do not posses significant radial velocity data. The obtained ephemerides are of very high precision and at least seven years ‘fresher’ than archival ephemerides. In particular, significantly reduced period uncertainties for Kepler-411d, Kepler-538b, and the candidates K00075.01/K00076.01 are reported. O–C diagrams were generated for all objects, with the most interesting ones discussed here. Updated TTV fits of five known multiplanet systems with significant TTVs were also attempted (Kepler-18, Kepler-25, Kepler-51, Kepler-89, and Kepler-396), however these suffered from the comparative scarcity and dimness of these systems in TESS. Despite these difficulties, TESS has once again shown itself to be an incredibly powerful follow-up instrument as well as a planet-finder in its own right. Extension of the methods used in this paper to the 30 min-cadence TESS data and TESS extended mission has the potential to yield updated ephemerides of hundreds more systems in the future.

Highlights

Maintenance of planet ephemerides is crucial to further characterization of known planets
Ephemerides have been updated for 22 Kepler planets and 4 planet candidates using short-cadence data from the Transiting Exoplanet Survey Satellite
Transit times for individual transits were recovered by using an Markov Chain Monte Carlo (MCMC) fit of a transit model based on stacked Kepler transits

Summary

Introduction

Maintenance of planet ephemerides is crucial to further characterization of known planets This is especially true for follow-up with highprofile observatories such as the upcoming James Webb Space Telescope (JWST; Gardner et al 2006), where timing uncertainties of less than 30 min are desirable (Dragomir et al 2020). The original Kepler mission finished 2013 May 11 after the failure of two of the satellite’s reaction wheels, meaning that it has been over seven years since most of these planets have been observed. This observational gap, coupled with uncertainties in the periods and epochs of the Kepler transits, has led to many of the planet/candidate ephemerides becoming imprecise or ‘stale’

Methods

Results

Discussion

Conclusion