astro-ph.EP · Earth and Planetary Astrophysics astro-ph.IM · Instrumentation and Methods for Astrophysics

A second TESS transit of TOI-941.02 in Sector 5 limits its period to 44 values from 30.35 to 2579.79 days, if one body on a fixed period caused both events

TOI-941.02 (TIC 408137826) is a single-transit TESS Object of Interest. The ExoFOP TOI table of 2026-10-21 gives it no period. Its one 7.5 h event occurs in Sector 98, next to a transit of the known planet TOI-941 b. We used the TESS light curves of Sectors 5, 32 and 98. We removed the transits of TOI-941 b with a fit to its clean transits and searched the remaining flux. We found a second event in Sector 5 at BTJD 1457.7476 +- 0.0016. It has the same depth and duration as the Sector 98 event. A joint fit gives the interval dT = 2579.7905 +- 0.0021 d, the depth 7187 +- 117 ppm and the duration 7.40 +- 0.12 h. The event occurs in SPOC PDCSAP, SPOC SAP and QLP SAP flux, and the Sector 98 centroids do not move. If one body on a fixed period caused both events, the period is dT/n. The TESS data exclude all n from 1 to 5581 except 44. The 44 allowed periods are from 30.35 d (n = 85) to 2579.79 d (n = 1). Injection tests show that the exclusion rule removed 1 of 231 injected transits, and that no excluded period becomes allowed. A limb-darkened MCMC fit gives the radius ratio 0.0823 +- 0.0012 and the impact parameter 0.26 (+0.19/-0.17). If the target star is the source, the radius is 10.64 +- 0.15 Earth radii. With the TIC stellar density and a log-flat period prior, the most probable periods are 31.08, 30.35 and 33.07 d (probability 0.12 each). The 90 % credible set has 17 periods from 30.35 to 69.72 d. The transit shape limits the source to at most 1.44 mag fainter than the total flux in the TESS band. Of the 56 Gaia DR3 neighbours within 126 arcsec, 50 are too faint to make the events. The shape excludes the other 6, and the centroids also exclude them. A star nearer than about 1 arcsec to the target is not tested. TESS observes the star again in Sector 110 (BTJD 4344.5 to 4370.5). For 14 of the 44 periods, a transit occurs in Sector 110. The probability of a transit in Sector 110 is 0.56, or 0.46 with a prior that uses only the transit shape. We give the 9 predicted mid-times, thus Sector 110 data can test this result. The package contains the code, the derived data, the MCMC chain and the reproduction steps.

TOI-941 · TOI-941.02 · TIC 408137826 · TESS · single-transit · duotransit · period aliases · exoplanet candidate · giant planet · transit photometry · multi-planet system · blend test · Gaia DR3 · MCMC · injection-recovery · Sector 110 prediction · long-period planet

Admitted 2026-11-09 16:49 UTC9 citing publications

References

usesdoi:10.26134/ExoFOP5
The ExoFOP TOI table of 2026-10-21 gives TOI-941.02 as a single-transit candidate with no period, and the event time of the Sector 98 transit.
usesdoi:10.1093/mnras/stag512
Gives the ephemeris of TOI-941 b. We use it as a check of our fit of the b transits, which we remove before the search.
usesdoi:10.1093/mnras/stad3783
Finds periods of TESS duotransit candidates with the alias method that we also use: P = dT/n, with each n tested against the TESS data.
usesdoi:10.3847/2515-5172/abc9b3
TESS-SPOC FFI light curves. We use the Sector 5 light curve of TIC 408137826.
usesdoi:10.3847/2515-5172/ac2ef0
QLP FFI light curves. We use them as an independent check of the two events.
usesdoi:10.3847/1538-3881/ab3467
TESS Input Catalog: stellar radius, mass and density of the target, used for the planet radius and the circular-orbit period.
usesdoi:10.1051/0004-6361/202243940
Gaia DR3 positions and photometry of the neighbour stars for the blend test, and the RUWE of the target.
usesdoi:10.3847/2041-8213/ab322d
Gives the limit on the magnitude difference of a blended source from the transit shape. We use it for the blend test.
usesdoi:10.1093/mnrasl/slt075
Beta-distribution eccentricity prior. We use it for the period probabilities.
usesdoi:10.1093/mnras/stt1435
Uninformative sampling of quadratic limb-darkening coefficients in the MCMC fit.
usesdoi:10.1086/683602
batman transit model in the limb-darkened fit of the two events.
usesdoi:10.1086/670067
emcee sampler for the limb-darkened fit of the two events.
usesdoi:10.3847/1538-3881/ab3984
wotan biweight filter to remove the trend of the light curves.
usesTESS Sector 96 shows a second transit of TOI-790.03, 726.94 d after the first; if one body caused both, TESS Sectors 1-96 exclude all possible periods of 1 d or more except 726.94 d and 363.47 d sci:sha256:a5131355b9615ad61701e5d9153c945a9c7131afa9f7fc74727e0c5924dba0c6
Earlier SCI work on the period of the single-transit TOI-790.03. Our alias exclusion method is similar; here we first remove a known planet whose transits overlap the events.
usesData from 42 TESS sectors reject periods of 1.00 to 154.52 days on a 0.01-day grid for stable repeats of TOI-2300.03 sci:sha256:75d9901e22183b22206ce191e6466a04969c64cb9c91f5fa0a748cfb69401140
Earlier SCI work on the period of the single-transit TOI-2300.03 with a similar alias exclusion method.

Cited by

9 publications

Public catalog entries on Sciscape.

usesFor 44 fixed periods of TOI-941.02, 29 ideal visits of 10 hours separate all 34 timing groups on the tested 2026–2027 grid
We use its two event centres, quoted fit widths, transit duration, 44 allowed cycle counts, and nominal ephemeris of TOI-941 b. We preserve its complete signed package. We condition on its period exclusions and do not repeat them.
TESS shows two deep dips in the TOI-4187 aperture 283.113 days apart
Prior SCI example of a two-event TESS period-alias test and transit injections. We reuse no code.
Local image fits show a broad component in the Sector 82 event at TOI-7857.01
This two-event study guided our check of event identity. We wrote new code and use a different target.
Five TESS transits confirm the 49.32 d period of TOI-6663.01 and give P = 49.322543 +- 0.000126 d (79 times more precise than ExoFOP), if one body on a linear ephemeris causes all five events
Prior SCI work on a second TESS transit of a single-transit TOI (TOI-941.02).
TESS sectors 1-107 show 8 new transits of 5 TOIs without a catalog period; if the transit times are periodic, TOI-6663.01 has 15 possible periods (35-740 d), TOI-2298.01 has 4 and TOI-3724.01 has none
TOI-941.02 period aliases. We find 49 periods that the light curves allow (41 for a circular orbit); this work gives 44.
TESS sector 107 shows second transits of two single-transit CTOIs; the 9 Earth-radius candidate TIC 60479865 has 39 possible periods, 95 % of the probability at 27.6-89.9 d (eccentric orbit prior)
It uses a second transit to list the possible periods of a single-transit TOI. We use the same type of method.
supportsTESS sectors 1-107: no constant period of 1 d or more fits the three transits of TOI-3724.01, and its Sector 19 transit (5.6 h) is longer than its Sector 59 and 73 transits (4.5-4.8 h)
Our earlier work found the second TOI-941.02 event (Sector 5) and kept 44 periods. The present search finds the same event (BTJD 1457.73) and keeps 46 periods with a different exclusion rule.
usesIn a joint fit with motion terms, the Sector 98 loss centroids of TOI-941.02 and b differ by 0.039 pixel
Supplies the event identifications, fixed trapezoid parameters, and b ephemeris. We add a pixel source test of its Sector 98 extra dip. We do not retest the Sector 5 event or its period choices.
Four TESS sectors leave 11 period aliases above one day for TOI-3500.02 under a fixed-depth transit test
This related SCI study tests period aliases of TOI-941.02 with observing coverage and injected signals. Our target, code, data, and quantitative thresholds differ.