Identify the astrophysical source of the 3.78-day periodic signal

Identify whether the 3.78-day, 407-ppm periodic transit-like signal originates from TIC 402710280 or from the background star 3.5 arcseconds away.

Background

The light curve contains a second periodic signal with a period of 3.78371 days, a depth of 407 ± 26 ppm, and a duration of approximately 1.3 hours. Its phase remains coherent across approximately 650 cycles, but the difference-image centroid is insufficiently precise to separate the target from the nearby background star.

If the background star produces the signal, it would require an eclipse involving approximately 14% of that star’s light. The authors do not claim the signal as a planet candidate because its source remains unresolved; spatially resolving photometry of a transit would determine whether the signal belongs to the target or the background object.

References

The light curve also contains a $407 \pm 26$~ppm signal with a period of 3.78~days whose source, the target or the background star, the present data cannot identify.

— A 36.34-day Sub-Neptune Candidate Transiting the Nearby K Dwarf TIC 402710280  (2610.26056 - Vora, 19 Oct 2026) in Abstract; see also Section 6, “A Second Periodic Signal” (Section \ref{sec:second})