Astronomers Discover Rare Quadruple Star System Consisting Of Two Eclipsing Binaries (Planetary Science)

A team of international astronomers reported on the discovery of a compact, coplanar, quadruply-lined, eclipsing quadruple star system from TESS data, TIC 454140642, also known as TYC 0074-01254-1. Their study recently appeared in Arxiv.

Most multiple star systems are triple stars. Systems with four or more components (also called quadruple) are less likely to occur. But, though they have lower occurence rates than the triple systems, the larger outer orbit is necessary for stability in the latter (triple) systems. This long outer orbital period reduces the probability of identification of the tertiary eclipses or occultations of a triple systems in TESS data. While such triples can (and do) produce multiple tertiary eclipses or occultations during one conjunction of the outer orbit in a single sector of TESS data, detecting multiple such conjunctions in one sector of data is highly unlikely. In turn, this makes determining the outer period of such triples – and thus the overall configuration of the respective system – challenging. In contrast, quadruple systems do not need to be at a conjunction of the outer orbit to reveal their nature, and eclipses/occultations of their constituent binaries can (and do) easily occur in a single sector of TESS data.

“We presented the discovery of the quadruple star TIC 454140642 that exhibit 4 sets of eclipses as well as prominent, dynamically induced apsidal motion and short-term four body perturbations”

The target was first observed by TESS in Sector 5 (at 30-min cadence) and again in Sector 32 (in 10-min cadence), and exhibited four sets of eclipses associated with two binary stars (A and B). Additional spectroscopic and photometric measurements reveal divergent radial velocities, eclipse-time variations and apsidal motion for both binaries, confirming that they form a gravitationally-bound quadruple system with a 2+2 hierarchy.

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Table 1: Median values of the parameters from the double EB simultaneous lightcurve, 2× SB2 radial velocity, double ETV, joint SED and PARSEC evolutionary track solution from Lightcurvefactory © Veselin Kostov et al.

The two binary stars have orbital periods of PA = 13.62 days and PB = 10.39 days, respectively, and slightly eccentric orbits (eA = 0.07, eB = 0.03). The four stars are very similar in terms of mass (individual masses between 1.105M and 1.195M), size (radii between 1.09R and 1.26R), and effective temperature (between 6188 K and 6434 K) (refer Table 1 to more parameters). The quadruple has an orbital period of PAB = 432 days and an eccentricity of eAB = 0.32. The entire system is essentially coplanar – the orbits of the two binaries and the wide orbit are aligned to within a fraction of a degree.

Finally, they concluded that, TIC 454140642 is the newest addition to the small family of confirmed, well-characterized, multiply-eclipsing quadruple systems.

Featured image: Structure of TIC 454140642, a quadruple star system consisting of two eclipsing binaries. © Veselin Kostov et al.

Reference: Veselin B. Kostov, Brian P. Powell, Guillermo Torres, Tamas Borkovits, Saul A. Rappaport, Andrei Tokovinin, Petr Zasche, David Anderson, Thomas Barclay, Perry Berlind, Peyton Brown, Michael L. Calkins, Karen A. Collins, Kevin I. Collins, Dennis M. Conti, Gilbert A. Esquerdo, Coel Hellier, Eric L. N. Jensen, Jacob Kamler, Ethan Kruse, David W. Latham, Martin Masek, Felipe Murgas, Greg Olmschenk, Jerome A. Orosz, Andras Pal, Enric Palle, Richard P. Schwarz, Chris Stockdale, Daniel Tamayo, Robert Uhlar, William F. Welsh, Richard West, “TIC 454140642: A Compact, Coplanar, Quadruple-lined Quadruple Star System Consisting of Two Eclipsing Binaries”, Arxiv, pp. 1-25, 2021.

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