TIC 258204238
An uncatalogued eclipsing-binary candidate from TESS.
Eclipsing-binary candidate: 0.6870-day period, a 1.67% primary eclipse. Automated cross-checks question this period - see below.
TIC 258204238 is a candidate eclipsing binary star with an orbital period of 0.6870 days, detected through automated analysis of TESS photometry. The primary eclipse produces a dimming of 1.13 percent, with a very strong detection signal-to-noise ratio of 692.6 in the box least-squares periodogram search. Pixel-level image analysis confirms the signal at the target location with a peak signal-to-noise of 13.5, though the centroid shows a 2.2 arcsecond offset from the catalog position. No secondary eclipse was detected in the data. This candidate does not appear in any of six major variable-star catalogs, making it a novel candidate from the automated pipeline. The machine-learning classifier assigns it a score of 0.45, indicating moderate likelihood of being a real eclipsing system rather than an instrumental artifact or false positive.
- Surface brightness ratio
- companion faint - no secondary eclipse
- Companion / star radius
- ~0.13
- Face hidden at primary eclipse
- ~2%
- Separation
- ~1.3 x the star's radius
- Eccentricity
- consistent with circular
Zoomed: both stars drawn about 0x 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 (5,607 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 2,473x 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 11:54 UTC
- Secondary2026-10-19 20:09 UTC
- Primary2026-10-20 04:24 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 1.043% (observed minus binned median).
Automated cross-checks question this period - see Caveats below.
- Period
- 0.68704 d
- Primary depth
- 1.67%
- Epoch (T0)
- 1683.786 BTJD
- Duration
- 8.40 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 40.
- 13.5
- 0.10 px2"
- 0.0475 phase
- TIC 2582042360.94 px, dT 4.0
- 0.86
- 40
The dimming is centred on the target star. No nearby contaminant detected.
- Centroid offset
- 0.10 px
- Difference SNR
- 13.5
- Capable neighbour
- TIC 258204236
- TESS sector
- 40
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
- 0.68704 d
- BLS period
- 0.68704 d
- Odd/even z
- 0.01
Caveats
Known limitations and things to check.
Cross-check:No eclipse at 76 of 225 covered epochs where the 0.68704 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
- 0.68704 d
- 0.68704 dsame
- 1.67% +/- 0.05%seen 60/225
- ML screening score
- 0.451logistic_regression
- -
- 0.01< 3
- 0.6870 dpower 0.32
- 8.4 h
- Distance (TIC, Gaia-based)
- 348 pc+/- 4
- 12.04 / 11.55
- 5607 K / 1.33 Rsun
- RA / Dec (J2000)
- 18h 51m 44.8s +39d 57m 33s
- 692.6 / 13.5
- 16,951 ptsover 1113 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 = 0.01 (gate 3.0): alternate eclipses match, so the BLS period stands.
O - C timing
60 eclipses timed, rms 62.82 min, reduced chi-square 4157.24 (58 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 = 0.687043 +/- 0.000001 d.