We have discovered a doubly eclipsing , bound , quadruple star system in the field of K2 Campaign 7 .
EPIC 219217635 is a stellar image with Kp = 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 followup radial-velocity ( ‘ RV ’ ) spectroscopy observations , adaptive optics imaging , as well as 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-year interval , corresponding to an acceleration , \dot { \gamma } = 0.0024 \pm 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 ^ { \circ } .
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 .