TIC 229146166
An uncatalogued eclipsing-binary candidate from TESS.
Eclipsing-binary candidate: 3.9903-day period (twice the BLS period), a 15.89% primary eclipse, a 15.54% secondary eclipse at phase 0.499. Automated cross-checks question this period - see below.
TIC 229146166 is a candidate eclipsing binary star detected in TESS photometry with an orbital period of 3.990257 days and a primary eclipse depth of 15.43 percent dimming. The detection shows a strong automated signal with a BLS signal-to-noise ratio of 446.3, and pixel-level image analysis confirms the eclipsing signature at the target location with a difference-imaging peak signal-to-noise of 46.2. However, the data exhibits a notable quirk: alternating eclipses differ significantly in depth, which may indicate systematic effects in the observations. The candidate does not appear in six major variable-star catalogs, making it potentially novel. No secondary eclipse was detected in the available data.
- Surface brightness ratio
- 0.98
- Companion temperature
- ~3,724 K
- Companion / star radius
- ~0.43
- Face hidden at primary eclipse
- ~19%
- Separation
- ~31 x the star's radius
- Eccentricity
- consistent with circular
- Secondary eclipse phase
- 0.499 measured, 0.500 in this orbit
Zoomed: both stars drawn about 6x larger than their real size relative to the orbit, so they overlap for longer than the real eclipse lasts. A star's surface never gets dimmer during an eclipse - part of it is simply hidden. What drops is the total light we receive, shown exactly by the readout and bar below from the real light curve; the glow dims with it, exaggerated so small dips show. Colours follow temperature on a stellar colour scale, saturated so the differences show; the star's is its catalogue value (3,740 K). The companion's colour, sizes and orbit shape are estimates from the eclipse depths, duration and timing, assuming central eclipses and spherical stars - good to perhaps tens of percent. Only the relative orbit is shown; both stars really circle their common centre of mass. Animated about 14,365x faster than real on average, slowing down through each eclipse, and starting from where the system is in its orbit right now. Hover to pause.
- Primary2026-10-19 21:48 UTC
- Secondary2026-10-21 21:36 UTC
- Primary2026-10-23 21:34 UTC
Computed from the fitted ephemeris. Approximate - not corrected for your location or for light-travel time across Earth's orbit.
The signal
A repeating, consistent dip in brightness.
Residual scatter 1.188% (observed minus binned median).
Automated cross-checks question this period - see Caveats below.
- Period
- 3.99026 d
- Primary depth
- 15.89%
- Secondary depth
- 15.54%
- Epoch (T0)
- 1356.677 BTJD
- Duration
- 1.39 h
The catalog check
Cross-matched against known variable-star catalogs to rule out anything already listed.
- VSXNot found
- ASAS-SNNot found
- Gaia eclipsing-binary tableNot found
- Gaia variable classificationNot found
- TESS EB catalog (Prsa+2022)Not found
- ExoFOP TOI listNot found
0/6 catalogs list a known variable at this position.
No known variable star or catalogued match at this position.
- Catalogs checked
- 6
- Matches
- 0
The pixel check
Confirms the dimming is on the target star, not a nearby source.
Out/in share one sqrt colour scale; in-eclipse = out-of-eclipse minus difference. TESS sector 2.
- 46.2
- 0.16 px3"
- 0.0000 phase
- none
- 0.76
- 2
The dimming is centred on the target star. No nearby contaminant detected.
- Centroid offset
- 0.16 px
- Difference SNR
- 46.2
- Capable neighbour
- none
- TESS sector
- 2
The Gaia view
A second spacecraft's measurements: how far away the star is, how bright and what colour, and whether its position fits a single star.
It is about 701 light years away: the light TESS recorded left it around 701 years ago.
Together the two stars give off about 19.6 times less light than the Sun in Gaia's band, before correcting for interstellar dust.
Its colour is redder than the Sun's, which usually means cooler - though dust along the way also reddens light.
Source: ESA Gaia DR3, source 4940735802417465216.
Gaia's measurements fit a single point of light well (RUWE 1.00), as expected for a pair too close for Gaia to separate.
- Distance
- 215 +/- 1 pc
- Light-travel time
- ~701 years
- Apparent G
- 14.56
- Absolute G
- 7.90
- Colour BP-RP
- 2.19
- RUWE
- 1.00
- Match offset
- 0.64 arcsec
The ground-survey check
An independent instrument, different years: does real ZTF photometry show the eclipse at the period TESS measured?
No ZTF observations at this position (declination -50.3 deg) - likely too far south for ZTF's footprint, which covers the sky north of roughly -31 deg. Not a mark against the candidate, just a gap in ground-survey coverage.
Fold it yourself
Adjust the period and watch the eclipse appear.
Shown at the true period. The raw light curve needed to re-fold at other periods has not been exported yet - this slider unlocks automatically once it is.
The period the pipeline measured. Drag the slider away from it and the eclipse smears out.
- True period
- 3.99026 d
- BLS period
- 1.99513 d
- Odd/even z
- 10.40
Caveats
Known limitations and things to check.
Cross-check:Eclipse duration (1.39 h) is too short relative to this light curve's ~30-minute cadence for any single predicted eclipse to hold enough points to measure on its own. The primary depth below is the whole-light-curve fold measurement from the vetting step, not a per-epoch one.
- Period alias:Odd/even eclipse-depth z-score is 10.40 (gate > 3.0): alternating eclipses differ significantly in depth, the signature of a true period double what BLS found. Pixel-check confirmation and eclipse timing are unaffected - report the corrected period, 3.990257 d, in any write-up.
VIIIInstrument
Raw values, fits and technical details.
Instrument
Raw values, fits and technical details.
Full statistics
- 3.99026 d
- 1.99513 dalias
- 15.89% +/- 0.15%seen 0/0
- ML screening score
- 0.449logistic_regression
- 15.54% +/- 0.26%phase 0.499, 60 sigma
- 10.40> 3: alias
- 1.9939 dpower 0.09
- 1.4 h
- Distance (TIC, Gaia-based)
- 216 pc+/- 1
- 14.58 / 13.60
- 3740 K / 0.78 Rsun
- RA / Dec (J2000)
- 01h 48m 23.6s -50d 18m 44s
- 446.3 / 46.2
- 1,826 ptsover 52 d
Eclipse close-ups
Same flux scale on both panels. Line: binned median. Shown in place of an orbit animation - this pipeline measures eclipses, it does not fit an orbit.
Period alias analysis
Odd/even depth z = 10.40 (gate 3.0): alternate eclipses differ, so the true period is 2 x 1.9951 = 3.9903 d.