TIC 290061484: A Triply Eclipsing Triple System with the Shortest Known Outer Period of 24.5 Days

Kavli Affiliate: Andrew Vanderburg

| First 5 Authors: Veselin B. Kostov, Saul A. Rappaport, Tamas Borkovits, Brian P. Powell, Robert Gagliano

| Summary:

We have discovered a triply eclipsing triple-star system, TIC 290061484, with
the shortest known outer period, Pout, of only 24.5 days. This "eclipses" the
previous record set by lambda Tauri at 33.02 days, which held for 68 yr. The
inner binary, with an orbital period of Pin = 1.8 days, produces primary and
secondary eclipses and exhibits prominent eclipse timing variations with the
same periodicity as the outer orbit. The tertiary star eclipses, and is
eclipsed by, the inner binary with pronounced asymmetric profiles. The
inclinations of both orbits evolve on observable timescales such that the
third-body eclipses exhibit dramatic depth variations in TESS data. A
photodynamical model provides a complete solution for all orbital and physical
parameters of the triple system, showing that the three stars have masses of
6.85, 6.11, and 7.90 MSun, radii near those corresponding to the main sequence,
and Teff in the range of 21,000-23,700 K. Remarkably, the model shows that the
triple is in fact a subsystem of a hierarchical 2+1+1 quadruple with a distant
fourth star. The outermost star has a period of ~3200 days and a mass
comparable to the stars in the inner triple. In ~20 Myr, all three components
of the triple subsystem will merge, undergo a Type II supernova explosion, and
leave a single remnant neutron star. At the time of writing, TIC 290061484 is
the most compact triple system and one of the tighter known compact triples
(i.e., Pout/Pin = 13.7).

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