52 Eclipsing Quadruple Star Candidates Discovered in TESS Full Frame Images

TL;DR

This work tackles the challenge of identifying eclipsing 2+2 quadruple stars in large time-series surveys by combining a machine-learning–driven initial search with intensive citizen-science vetting. A rigorous validation pipeline—pixel-level checks, photocenter/difference-imaging, and Gaia-based astrometric indicators—ensures on-target origins for two eclipsing binaries within each system and mitigates false positives. The authors derive precise ephemerides and eclipse properties using flexible light-curve models and extract eclipse timing variations to reveal dynamical interactions, including LTTE in several cases. The 52 newly vetted 2+2 quadruple candidates bring the TGV catalog to 250, with some sources having Gaia outer-orbit solutions and a broad range of orbital configurations, enabling robust statistical studies of formation and long-term dynamical evolution in hierarchical multiple systems.

Abstract

We present the discovery of 52 eclipsing quadruple star candidates detected in TESS Full Frame Image eleanor data by machine learning and citizen scientists. The uniformly-vetted and -validated targets exhibit two sets of eclipses following two distinct periods, representing quadruple systems with a 2+2 hierarchical configuration. Detailed photocenter measurements confirmed that both sets of eclipses originate within ~0.1-0.2 pixels (~2-4 arcsec) of the corresponding target, and ruled out resolved nearby field stars. The catalog includes a number of systems producing prominent eclipse timing variations and/or apsidal motion, a quadruple with an outer period of ~1,400 days, and even a 2+2 quadruple in a likely wide quintuple with a resolved co-moving star. Additionally, two systems have complete astrometric solutions for the outer orbits from Gaia. We provide the measured ephemerides, eclipse depths and durations, overall statistical properties, and highlight potentially interesting systems that merit further investigations.

Figures (14)

• Figure 1: An illustrative example of an eclipsing quadruple candidate detected in TESS FFI eleanor data. The panels show six sectors of data for TIC 64832327, exhibiting two sets of primary eclipses with two distinct periods, labeled as PAprim (13 red events) and PBprim (6 blue events).
• Figure 6: Upper and middle panels: Generalized Gaussian model fits (red) for the primary eclipses of the PA $\approx$ 3.96 days component (upper) and PB $\approx$ 4.94 days (middle) component of the quadruple candidate TIC 20938739. The black dots represent the TESS FFI data for Sector 51. The two eclipses have notably different shapes -- one being more V-shaped and the other more U-shaped -- yet the model fits both. Lower panel: phase-folded primary eclipses of the PA $\approx$ 3.08 days component of the quadruple candidate TIC 97642729 showing TESS FFI data for all available Sectors (6, 33, 43, 44, 45, 72, and 87). Due to systematic effects, the apparent eclipse depths vary dramatically between different sectors.
• Figure 7: TIC 99629496: an example of systematics-dominated eleanor lightcurve where the eclipses are upside down in one sector of TESS data.
• Figure 8: Measured anti-correlated ETVs for the PA $\approx$ 4.86-days component (left panel, primary eclipses) and PB $\approx$ 8.17 days components (right panel, primary (red) and secondary (blue) eclipses) for TIC 48089827. The two EBs produce dramatic, anti-correlated ETVs that confirm the target as a genuine quadruple system. The solid curves represent the best-fit models indicating that the ETVs are dominated by the light travel time effect, and suggesting an outer period of about 1,400 days.
• Figure 9: Upper left panel: Sky position in RA and Dec for the 52 quadruple candidates presented here (red stars). The black dots represent the other 198 targets in the TGV catalog, and the blue line represents the Galactic plane. Upper right: Corresponding Gaia DR3 composite effective temperature as a function of TESS magnitude. Lower panels: Gaia DR3 Astrometric Excess Noise (AEN), Astrometric Excess Noise Sig (AENS), and Renormalized Unit Weight Error (RUWE); AEN and AENS are in units of milliarcsec. Note the axes are in log10 base. The dashed vertical line in the right panel represents RUWE = 1.4, a potential indicator for unresolved companions.