TIC 308574817
An uncatalogued eclipsing-binary candidate from TESS.
Eclipsing-binary candidate: 4.6444-day period (twice the BLS period), a 18.96% primary eclipse, a 7.76% secondary eclipse at phase 0.499.
TIC 308574817 is a candidate eclipsing binary star with an orbital period of 4.6 days, detected in automated TESS photometry data. The system shows a primary eclipse with a dimming depth of 11.30 percent, while no secondary eclipse was detected. The transit signal achieved a high detection significance of 132.8 in the BLS analysis, and pixel-level difference imaging confirmed the signal at the target location with a peak signal-to-noise of 23.8, though the centroid offset of 0.7 arcseconds warrants note. The candidate does not appear in six major variable-star catalogs. However, a data quality flag indicates that alternating eclipse depths differ significantly, suggesting the true orbital period may be double the initial measurement. Despite this period ambiguity, pixel-level confirmation and eclipse timing remain consistent with the corrected 4.6-day period reported here.
- Surface brightness ratio
- 0.41
- Companion temperature
- ~5,376 K
- Companion / star radius
- ~0.45
- Face hidden at primary eclipse
- ~21%
- Separation
- ~18 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 4x 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 (7,154 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 16,720x 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 09:00 UTC
- Secondary2026-10-21 16:40 UTC
- Primary2026-10-24 00:28 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 9.744% (observed minus binned median).
Alternate eclipses differ in depth, so the true period is twice the search period.
- Period
- 4.64440 d
- Primary depth
- 18.96%
- Secondary depth
- 7.76%
- Epoch (T0)
- 1471.925 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 6.
- 23.8
- 0.03 px1"
- -0.0050 phase
- TIC 3085748021.61 px, dT 1.6
- 0.83
- 6
The dimming is centred on the target star. No nearby contaminant detected.
- Centroid offset
- 0.03 px
- Difference SNR
- 23.8
- Capable neighbour
- TIC 308574802
- TESS sector
- 6
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
- 4.64440 d
- BLS period
- 2.32220 d
- Odd/even z
- 4.33
Caveats
Known limitations and things to check.
- Period alias:Odd/even eclipse-depth z-score is 4.33 (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, 4.644399 d, in any write-up.
VIIIInstrument
Raw values, fits and technical details.
Instrument
Raw values, fits and technical details.
Full statistics
- 4.64440 d
- 2.32220 dalias
- 18.96% +/- 0.57%seen 3/3
- ML screening score
- 0.132logistic_regression
- 7.76% +/- 0.50%phase 0.499, 16 sigma
- 4.33> 3: alias
- 1.1631 dpower 0.04
- 2.9 h
- Distance (TIC, Gaia-based)
- 2644 pc+/- 333
- 15.07 / 14.67
- 7154 K / 1.99 Rsun
- RA / Dec (J2000)
- 06h 40m 0.2s +13d 59m 57s
- 132.8 / 23.8
- 904 ptsover 22 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 = 4.33 (gate 3.0): alternate eclipses differ, so the true period is 2 x 2.3222 = 4.6444 d.
O - C timing
3 eclipses timed, rms 1.84 min, reduced chi-square 0.37 (1 dof): consistent with a constant period.
Each eclipse timed by fitting the star's own mean eclipse profile; fitted P = 4.642643 +/- 0.002775 d.