TIC 257747010
An uncatalogued eclipsing-binary candidate from TESS.
Eclipsing-binary candidate: 4.2348-day period (twice the BLS period), a 32.37% primary eclipse, a 31.17% secondary eclipse at phase 0.502.
TIC 257747010 is a candidate eclipsing binary star with an orbital period of 4.234848 days, identified through automated analysis of TESS photometry. The primary eclipse produces a 25.38% dimming, while a secondary eclipse was detected at 5.7 sigma significance. Pixel-level difference imaging confirms the signal originates from the target location, with a peak signal-to-noise ratio of 112.4. However, data quality analysis reveals that alternating eclipses differ significantly in depth, suggesting the initial period estimate was half the true value. The candidate does not appear in six major variable-star catalogs, making it a novel find, though the machine-learning screening score of 0.45 indicates moderate confidence in its validity as a real eclipsing system.
- Surface brightness ratio
- 0.96
- Companion temperature
- ~3,623 K
- Companion / star radius
- ~0.69
- Face hidden at primary eclipse
- ~47%
- Separation
- ~27 x the star's radius
- Eccentricity
- consistent with circular
- Secondary eclipse phase
- 0.502 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 (3,650 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 15,245x 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.
- Secondary2026-10-20 03:33 UTC
- Primary2026-10-22 06:07 UTC
- Secondary2026-10-24 09:11 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 3.841% (observed minus binned median).
Alternate eclipses differ in depth, so the true period is twice the search period.
- Period
- 4.23485 d
- Primary depth
- 32.37%
- Secondary depth
- 31.17%
- Epoch (T0)
- 2798.505 BTJD
- Duration
- 2.02 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 82.
- 112.4
- 0.05 px1"
- 0.0100 phase
- TIC 2829449032.26 px, dT -2.7
- 0.71
- 82
The dimming is centred on the target star. No nearby contaminant detected.
- Centroid offset
- 0.05 px
- Difference SNR
- 112.4
- Capable neighbour
- TIC 282944903
- TESS sector
- 82
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?
- ZTF g (707 pts, 32 outliers)Not significant (p=0.01)
- ZTF i (223 pts, 14 outliers)Not significant (p=0.02)
- ZTF r (1046 pts, 57 outliers)Confirmed (p=0.0079)
Folded at the TESS-measured period of 2.11742 d, at least one band shows individual ZTF epochs - real observations, years apart - landing far below the baseline brightness and clustered in phase far tighter than chance would produce given how many such epochs that band has (p < 0.01, chance-corrected for the outlier count).
Source: ZTF public light-curve archive (IRSA), independent of the TESS data used to detect this candidate.
Real ZTF ground-survey photometry backs this period: one band shows epochs, years apart, landing more than 5 sigma below the baseline brightness and clustered in phase far tighter than chance would produce given how many such epochs that band has (p < 0.01) - a different instrument finding the same eclipse.
- Bands confirmed
- ZTF r
- Deepest clustered dip
- 38.9 sigma (ZTF r)
- Chance p-value
- 0.0079 (ZTF r)
- Period tested
- 2.11742 d
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
- 4.23485 d
- BLS period
- 2.11742 d
- Odd/even z
- 7.66
Caveats
Known limitations and things to check.
- Period alias:Odd/even eclipse-depth z-score is 7.66 (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, 4.234848 d, in any write-up.
VIIIInstrument
Raw values, fits and technical details.
Instrument
Raw values, fits and technical details.
Full statistics
- 4.23485 d
- 2.11742 dalias
- 32.37% +/- 0.59%seen 12/12
- ML screening score
- 0.450logistic_regression
- 31.17% +/- 0.26%phase 0.502, 119 sigma
- 7.66> 3: alias
- 0.5294 dpower 0.06
- 2.0 h
- Distance (TIC, Gaia-based)
- 368 pc+/- 7
- 15.68 / 14.60
- 3650 K / 0.70 Rsun
- RA / Dec (J2000)
- 21h 21m 19.5s +21d 51m 2s
- 208.1 / 112.4
- 14,297 ptsover 762 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 = 7.67 (gate 3.0): alternate eclipses differ, so the true period is 2 x 2.1174 = 4.2348 d.
O - C timing
12 eclipses timed, rms 0.60 min, reduced chi-square 0.78 (10 dof): consistent with a constant period.
Each eclipse timed by fitting the star's own mean eclipse profile; fitted P = 4.235041 +/- 0.000002 d.