CHEOPS Running Call: Approved Programmes

The programmes awarded observing time through the CHEOPS Running Call are listed below. This page will be updated following each completed evaluation batch.

Abstracts

PR270001 — Recovering the Lost Transit of a Resonant Companion in a 135 Myr Planetary System: A Continuous CHEOPS Stare to Enable a Rare TTV Mass (PI: Madyson Barber)
Young transiting planets provide direct probes of formation and evolutionary processes in action. Those in mean motion resonance (MMR) are especially valuable for photodynamical modeling, determining the planetary masses and orbital eccentricities. Due to strengthened stellar variability at young ages, observing transit timing variations (TTVs) in these young systems may be the best avenue for determining the planet masses. Here we propose to confirm planet candidate TIC 150070085 c, a second planet in 3:2 MMR with the validated 135 Myr TIC 150070085 b, which shows strong (>30-min amplitude) TTVs. Confirmation would unlock the ability to measure masses for planets at a critical age where very few systems have been discovered.

PR270002 — V471 Tau: Solving the mystery of eclipse-timing variations (PI: Ignasi Ribas)
V471 Tau is the prototype of pre-cataclysmic binaries and has displayed eclipse-timing variations for more than five decades. These have been attributed either to the light-travel time effect caused by a circumbinary companion or to magnetic-cycle-driven changes in the gravitational quadrupole moment of the K2 star. Despite an exceptional timing baseline, the underlying mechanism remains unresolved. We propose 16 CHEOPS visits at 10-s cadence to obtain a precisely sampled “super-eclipse” of this sharp, 49-min event. The combined light curve will deliver a new eclipse timing in 2026 and measure the ingress, egress, and total duration with uncertainties of order one second. This is the key new diagnostic: a pure light-travel time effect shifts all contact points equally and preserves the eclipse shape, whereas an Applegate–Lanza mechanism may alter the orbital velocity and impact parameter, producing measurable duration changes. Comparison with K2 and TESS eclipses will therefore provide the first direct test capable of discriminating between the two scenarios. CHEOPS can finally resolve one of the longest-standing puzzles in eclipse-timing studies and clarify whether V471 Tau hosts a substellar circumbinary companion or reveals magnetic restructuring of a close binary.

This page was last updated on 17 August 2026.