A CHEOPS Search for Massive, Long-Period Companions to the Warm Jupiter K2-139 b
Alexis M. S. Smith, Szilard Csizmadia

TL;DR
This study refines the orbital parameters of the warm Jupiter K2-139 b using CHEOPS and K2 data, enabling precise future transit predictions and constraining the presence of nearby massive companions.
Contribution
It provides improved ephemeris accuracy for K2-139 b and rules out the existence of massive companions within certain orbital periods, demonstrating the effectiveness of CHEOPS observations.
Findings
Transit ephemeris precision improved to less than 10 minutes for the next decade
No evidence of additional massive planets or brown dwarfs within 150 days or one year periods
Stellar spot configuration changed, with no spot-crossing events detected in CHEOPS data
Abstract
K2-139 b is a warm Jupiter with an orbital period of 28.4 d, but only three transits of this system have previously been observed, in the long-cadence mode of K2, limiting the precision with which the orbital period can be determined, and future transits predicted. We report photometric observations of four transits of K2-139 b with ESA's CHaracterising ExOPlanet Satellite (CHEOPS), conducted with the goal of measuring the orbital obliquity via spot-crossing events. We jointly fit these CHEOPS data alongside the three previously-published transits from the K2 mission, considerably increasing the precision of the ephemeris of K2-139 b. The transit times for this system can now be predicted for the next decade with a precision less than 10 minutes, compared to over one hour previously, allowing the efficient scheduling of observations with Ariel. We detect no significant…
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