2018MNRAS.478.5135B

We have discovered a doubly eclipsing, bound, quadruple star system in the field of K2 Campaign 7. EPIC 219217635 is a stellar image with K_p = 12.7 that contains an eclipsing binary (EB) with P_A = 3.59470 d and a second EB with P_B = 0.61825 d. We have obtained follow-up radial velocity (RV) spectroscopy observations, adaptive optics imaging, and ground-based photometric observations. From our analysis of all the observations, we derive good estimates for a number of the system parameters. We conclude that (1) both binaries are bound in a quadruple star system; (2) a linear trend to the RV curve of binary A is found over a 2-yr interval, corresponding to an acceleration, {dot}γ= 0.0024 ±0.0007 cm s^–2; (3) small irregular variations are seen in the eclipse timing variations (ETVs) detected over the same interval; (4) the orbital separation of the quadruple system is probably in the range of 8-25 au; and (5) the orbital planes of the two binaries must be inclined with respect to each other by at least 25°. In addition, we find that binary B is evolved, and the cooler and currently less massive star has transferred much of its envelope to the currently more massive star. We have also demonstrated that the system is sufficiently bright that the eclipses can be followed using small ground-based telescopes, and that this system may be profitably studied over the next decade when the outer orbit of the quadruple is expected to manifest itself in the ETV and/or RV curves.