TIC 273787849
An uncatalogued eclipsing-binary candidate from TESS.
Eclipsing-binary candidate: 2.1425-day period, a 3.11% primary eclipse, a 0.99% secondary eclipse at phase 0.510. Automated cross-checks question this period - see below.
TIC 273787849 is a candidate eclipsing binary star with an orbital period of 2.1425 days. TESS photometry reveals a primary eclipse causing the star to dim by 2.80%, detected with a signal-to-noise ratio of 402.7 using box least-squares analysis. No secondary eclipse was observed. Pixel-level image analysis confirms the dimming occurs at the target location, with a peak signal-to-noise of 36.4, though the centroid offset of 10.1 arcsec warrants attention. The candidate does not appear in six major variable-star catalogs, making it a novel find. The automated pipeline's machine-learning classifier assigned a score of 0.77 (on a scale where 1 indicates highest confidence), and the data passed all quality checks without flags.
- Surface brightness ratio
- 0.32
- Companion temperature
- ~4,426 K
- Companion / star radius
- ~0.18
- Face hidden at primary eclipse
- ~3%
- Separation
- ~9.6 x the star's radius
- Eccentricity
- at least 0.015
- Secondary eclipse phase
- 0.510 measured, 0.510 in this orbit
Zoomed: both stars drawn about 2x 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 (6,049 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 7,713x 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 23:09 UTC
- Secondary2026-10-21 01:22 UTC
- Primary2026-10-22 02:35 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 0.451% (observed minus binned median).
Automated cross-checks question this period - see Caveats below.
- Period
- 2.14255 d
- Primary depth
- 3.11%
- Secondary depth
- 0.99%
- Epoch (T0)
- 1327.468 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 39.
- 36.4
- 0.48 px10"
- 0.0250 phase
- TIC 2737878582.08 px, dT 3.5
- 0.81
- 39
The dimming is centred on the target star. No nearby contaminant detected.
- Centroid offset
- 0.48 px
- Difference SNR
- 36.4
- Capable neighbour
- TIC 273787858
- TESS sector
- 39
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.
It is about 2,179 light years away: the light TESS recorded left it around 2,179 years ago.
Together the two stars give off about 2.7 times the Sun's light in Gaia's band - before correcting for interstellar dust, which only makes distant stars look fainter.
Its colour is close to the Sun's.
Source: ESA Gaia DR3, source 4618432248115011328.
Gaia's measurements fit a single point of light well (RUWE 1.11), as expected for a pair too close for Gaia to separate.
- Distance
- 668 +/- 5 pc
- Light-travel time
- ~2,179 years
- Apparent G
- 12.72
- Absolute G
- 3.60
- Colour BP-RP
- 0.84
- RUWE
- 1.11
- Match offset
- 0.38 arcsec
The ground-survey check
An independent instrument, different years: does real ZTF photometry show the eclipse at the period TESS measured?
No ZTF observations at this position (declination -81.4 deg) - likely too far south for ZTF's footprint, which covers the sky north of roughly -31 deg. Not a mark against the candidate, just a gap in ground-survey coverage.
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
- 2.14255 d
- BLS period
- 2.14255 d
- Odd/even z
- 2.06
Caveats
Known limitations and things to check.
Cross-check:No eclipse at 12 of 32 covered epochs where the 2.14255 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
- 2.14255 d
- 2.14255 dsame
- 3.11% +/- 0.22%seen 29/32
- ML screening score
- 0.769logistic_regression
- 0.99% +/- 0.02%phase 0.510, 51 sigma
- 2.06< 3
- 1.0713 dpower 0.25
- 2.0 h
- Distance (TIC, Gaia-based)
- 656 pc+/- 9
- 12.73 / 12.28
- 6049 K / 1.62 Rsun
- RA / Dec (J2000)
- 01h 55m 20.2s -81d 26m 56s
- 402.7 / 36.4
- 12,286 ptsover 1064 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 = 2.06 (gate 3.0): alternate eclipses match, so the BLS period stands.
O - C timing
29 eclipses timed, rms 0.84 min, reduced chi-square 0.98 (27 dof): consistent with a constant period.
Each eclipse timed by fitting the star's own mean eclipse profile; fitted P = 2.142704 +/- 0.000002 d.