Eclipse Timing Variations of Circumbinary Substellar Objects in TESS Data

Abstract

Circumbinary planets and brown dwarfs form in complex gravitational environments, offering insights into formation, orbital stability, and habitability prospects. However, they remain underrepresented, with only 60 confirmed or candidate systems known. In this work, we leverage TESS photometry to search for circumbinary companions through eclipse timing variations (ETVs), analyzing 152 detached eclipsing binaries. By modeling eclipse timings, we identify 37 systems with significant periodic signals, 19 of which have false alarm probabilities below 0.01. One system, TIC 142979644, emerges as a promising candidate to host a circumbinary substellar companion, with estimated masses of $18.8~M_{\rm J}$ and $11.1~M_{\rm J}$ from different methods. Simulations using synthetic ETVs indicate a 5\% recovery rate for circumbinary brown dwarfs and 0.1\% for Jupiter-like planets, with median masses of $56.6^{+16.5}_{-23.4}~M_{\rm J}$ and periods of $1404^{+1361}_{-953}$ days. Our simulations show that the smallest detectable mass is $1.6~M_{\rm J}$ at a period of 1860 days and confirm that ETV methods are effective in detecting misaligned systems. In the absence of a detection, we set an upper limit of 40\% on the occurrence rate of circumbinary brown dwarfs at the 2$σ$ confidence level. In contrast, a confirmed single detection would imply an occurrence rate of 13.08\%. These constraints are consistent with previous abundance estimates for circumbinary brown dwarfs ($\lesssim6.5\%$). As most circumbinary substellar companions detected through ETVs are found around post-common envelope binaries, our recovery rate of 0.83\% in their progenitors implies that even a single detection would strongly favor a first-generation origin.