TIC 178331798
An uncatalogued eclipsing-binary candidate from TESS.
Eclipsing-binary candidate: 1.8205-day period, a 2.81% primary eclipse, a 0.74% secondary eclipse at phase 0.505. Automated cross-checks question this period - see below.
TIC 178331798 is a candidate eclipsing binary star with an orbital period of 1.8205 days. Automated analysis of TESS photometry detected a primary eclipse causing a 2.45% dimming of starlight, with a strong signal-to-noise ratio of 79.9 from the box-least-squares search algorithm. No secondary eclipse was detected. Pixel-level image analysis provided a difference-imaging confirmation with a signal-to-noise peak of 7.9, though the centroid offset measured 9.0 arcsec from the target. The candidate does not appear in six major variable-star catalogs, making it a previously unlisted object. The machine-learning screening score of 0.35 indicates moderate confidence that this represents a real stellar target. This candidate has passed all automated data quality checks.
- Surface brightness ratio
- 0.27
- Companion / star radius
- ~0.17
- Face hidden at primary eclipse
- ~3%
- Separation
- ~5.7 x the star's radius
- Eccentricity
- consistent with circular
- Secondary eclipse phase
- 0.505 measured, 0.500 in this orbit
Zoomed: both stars drawn about 1x 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 are illustrative. 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 6,554x 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.
- Secondary2026-10-19 10:21 UTC
- Primary2026-10-20 07:57 UTC
- Secondary2026-10-21 06:02 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 2.638% (observed minus binned median).
Automated cross-checks question this period - see Caveats below.
- Period
- 1.82052 d
- Primary depth
- 2.81%
- Secondary depth
- 0.74%
- Epoch (T0)
- 1492.004 BTJD
- Duration
- 2.88 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 7.
- 7.9
- 0.43 px9"
- -0.0025 phase
- TIC 1783318000.66 px, dT 1.1
- 0.96
- 7
The dimming is centred on the target star. No nearby contaminant detected.
- Centroid offset
- 0.43 px
- Difference SNR
- 7.9
- Capable neighbour
- TIC 178331800
- TESS sector
- 7
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.
The latest Gaia context file does not include this candidate yet, so there is no Gaia view to show.
The ground-survey check
An independent instrument, different years: does real ZTF photometry show the eclipse at the period TESS measured?
The latest ground-survey file does not include this candidate yet, so there is no independent ZTF check to show.
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
- 1.82052 d
- BLS period
- 1.82052 d
- Odd/even z
- 0.06
Caveats
Known limitations and things to check.
Cross-check:No eclipse at 1 of 14 covered epochs where the 1.82052 d period predicts one (each under half the typical depth, > 5 sigma below it). The period is probably wrong - the dips seen may be separate eclipses of a longer-period system.
VIIIInstrument
Raw values, fits and technical details.
Instrument
Raw values, fits and technical details.
Full statistics
- 1.82052 d
- 1.82052 dsame
- 2.81% +/- 0.08%seen 12/14
- ML screening score
- 0.347logistic_regression
- 0.74% +/- 0.06%phase 0.505, 13 sigma
- 0.06< 3
- 0.9010 dpower 0.06
- 2.9 h
- Distance (TIC, Gaia-based)
- 1932 pc
- 14.83 / 14.35
- - / -
- RA / Dec (J2000)
- 07h 13m 11.5s -09d 17m 27s
- 79.9 / 7.9
- 1,072 ptsover 24 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 = 0.06 (gate 3.0): alternate eclipses match, so the BLS period stands.
O - C timing
12 eclipses timed, rms 4.67 min, reduced chi-square 4.93 (10 dof): more scatter than the timing errors explain - worth a closer look.
Each eclipse timed by fitting the star's own mean eclipse profile; fitted P = 1.820506 +/- 0.000096 d.