Ole Romer's method still on the stage. The study of two bound eclipsing binaries in quintuple system V994 Her

TL;DR

This study confirms the quintuple nature of V994 Her, demonstrating that two eclipsing binaries orbit each other with a 6.3-year period using timing variations, and reveals their orbital eccentricities and apsidal motions.

Contribution

The paper provides the first detailed analysis confirming the gravitational binding and orbital parameters of the V994 Her system using eclipse timing variations.

Findings

V994 Her is a quintuple system with two eclipsing binaries.

The two binaries orbit each other with a period of about 6.3 years.

Both binaries exhibit slight orbital eccentricities and slow apsidal motions.

Abstract

More than three hundred years ago, Ole Romer measured the speed of light only by observing the periodic shifting of the observed eclipse arrival times of Jupiter's moons arising from the varying Earth-Jupiter distance. The same method of measuring the periodic modulation of delays is still used in astrophysics. The ideal laboratories for this effect are eclipsing binaries. The unique system V994 Her consists of two eclipsing binaries orbiting each other. However, until now it was not certain whether these are gravitationally bound and what their orbital period is. We show that the system is in fact quintuple and the two eclipsing binaries are orbiting each other with period about 6.3 years. This analysis was made only from studying the periodic modulation of the two periods, when during the periastron passage one binary has an apparently shorter period, while the other one longer, exactly as required by a theory. Additionally, it was found that both inner eclipsing pairs orbit with slightly eccentric orbits undergoing a slow apsidal motions with a period of the order of centuries.