TIC 219765539
An uncatalogued eclipsing-binary candidate from TESS.
Eclipsing-binary candidate: 1.3809-day period (twice the BLS period), a 0.10% primary eclipse, a 0.03% secondary eclipse at phase 0.232. Automated cross-checks question this period - see below.
TIC 219765539 is a candidate eclipsing binary star detected in TESS photometry with an orbital period of 1.380873 days and a primary eclipse depth of 0.03% dimming. The automated pipeline identified this system with a detection significance of 17.7 in the box-least-squares search. However, two data quality issues warrant attention: the odd and even eclipses show significantly different depths, which may indicate the true period is double what the initial search found, and the pixel-level centroid offset of 19.0 arcsec places the signal only marginally closer to the target star than to a nearby bright neighbor - within the pipeline's own systematic uncertainty of 0.10-0.3 pixels. The candidate does not appear in six checked variable-star catalogs. No secondary eclipse was detected, and the machine-learning screening score is 0.64 out of 1.0.
- Surface brightness ratio
- 0.33
- Companion temperature
- ~3,610 K
- Companion / star radius
- ~0.08
- Face hidden at primary eclipse
- ~1%
- Separation
- ~4.0 x the star's radius
- Eccentricity
- at least 0.421
- Secondary eclipse phase
- 0.232 measured, 0.240 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 follow temperature on a stellar colour scale, saturated so the differences show; the star's is its catalogue value (4,617 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 4,971x 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 07:22 UTC
- Primary2026-10-20 08:50 UTC
- Secondary2026-10-20 16:30 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 0.097% (observed minus binned median).
Automated cross-checks question this period - see Caveats below.
- Period
- 1.38087 d
- Primary depth
- 0.10%
- Secondary depth
- 0.03%
- Epoch (T0)
- 2581.541 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 47.
- 9.6
- 0.91 px19"
- 0.0025 phase
- TIC 14009558830.94 px, dT 8.4
- 0.96
- 47
The dimming centroid sits almost as close to a bright neighbour as to the target.
- Centroid offset
- 0.91 px
- Difference SNR
- 9.6
- Capable neighbour
- TIC 1400955883
- TESS sector
- 47
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
- 1.38087 d
- BLS period
- 0.69044 d
- Odd/even z
- 3.64
Caveats
Known limitations and things to check.
Cross-check:No eclipse at 6 of 17 covered epochs where the 1.38087 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.
- Period alias:Odd/even eclipse-depth z-score is 3.64 (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, 1.380873 d, in any write-up.
- Thin margin:The ON_TARGET call rests on a neighbour-competition margin of just 0.035 px (dimming centroid 0.906 px from target vs 0.941 px from the nearest bright-enough neighbour) - inside diag_pixel.py's own stated centroid systematic of 0.10-0.3 px. TESS's resolution cannot confidently separate this star from that neighbour.
VIIIInstrument
Raw values, fits and technical details.
Instrument
Raw values, fits and technical details.
Full statistics
- 1.38087 d
- 0.69044 dalias
- 0.10% +/- 0.01%seen 2/17
- ML screening score
- 0.643logistic_regression
- 0.03% +/- 0.00%phase 0.232, 9 sigma
- 3.64> 3: alias
- 0.3459 dpower 0.04
- 2.9 h
- Distance (TIC, Gaia-based)
- 826 pc+/- 17
- 10.48 / 9.81
- 4617 K / 10.21 Rsun
- RA / Dec (J2000)
- 17h 30m 49.6s +65d 45m 41s
- 17.7 / 9.6
- 16,935 ptsover 26 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 = 3.64 (gate 3.0): alternate eclipses differ, so the true period is 2 x 0.6904 = 1.3809 d.