2022ApJ...938..133P

We report the discovery with TESS of a remarkable quadruple star system with a 2+1+1 configuration. The two unique characteristics of this system are that (i) the inner eclipsing binary (stars Aa and Ab) eclipses the star in the outermost orbit (star C), and (ii) these outer fourth-body eclipses last for ∼12 days, the longest of any such system known. The three orbital periods are ∼3.3 days, ∼51 days, and ∼2100 days. The extremely long duration of the outer eclipses is due to the fact that star B slows binary A down on the sky relative to star C. We combine TESS photometric data, ground-based photometric observations, eclipse timing points, radial velocity measurements, the composite spectral energy distribution, and stellar isochrones in a spectrophotodynamical analysis to deduce all of the basic properties of the four stars (mass, radius, T_eff, and age), as well as the orbital parameters for all three orbits. The four masses are M_Aa = 0.382 M_⊙, M_Ab = 0.300 M_⊙, M_B = 0.540 M_⊙, and M_C = 0.615 M_⊙, with a typical uncertainty of 0.015 M_⊙.