Year: 2026
Type: preprint
Abstract: Transiting sub-Neptunes on orbits longer than a month are rare around bright stars. We report a candidate with a 36.34-day period around TIC 402710280, a $V = 10.0$ K dwarf at 66.8 pc that the Transiting Exoplanet Survey Satellite (TESS) has observed only in full-frame images. Four transits from 2021 to 2026, reduced by three independent pipelines, have consistent depths (mean $2092 \pm 47$ ppm) and a duration of $5.27 \pm 0.05$ h. Two are 36.36 days apart. The light curves exclude every shorter period consistent with both down to one day, and the duration disfavors still shorter ones, leaving $P = 36.33986 \pm 0.00051$ d. The candidate's radius is $3.75 \pm 0.22\,R_\oplus$ and its equilibrium temperature $498 \pm 21$ K. Difference-image centroids place the signal $1.5'' \pm 1.3''$ from the target, and eclipse models of the only nearby Gaia source, $3.5''$ away, fit worse than a planet by $Δχ^2 \geq 142$ for every main-sequence pair. TRICERATOPS gives a false-positive probability of $0.003 \pm 0.004$; without high-resolution imaging, the object remains a candidate. The transit times scatter about a linear ephemeris by 21.8 min (rms), and an independent reduction reproduces the largest departure. Four transits cannot separate timing systematics from transit-timing variations. A second signal, of $407 \pm 26$ ppm at 3.78 days, may come from the target, an unresolved companion, or the background star. We predict a transit in TESS Sector 114 on 2027 February 19.
Source: arXiv (Cornell University)
Author: Vora, Rishit
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7221931568