Eclipse Depth Variations in Seven Eclipsing Binaries as Observed by KELT and TESS

Abstract A set of eclipsing binary systems exhibit a changing inclination over time due to the gravitational influence of a third stellar companion. These changing inclinations manifest in photometric observations over time as eclipse depth variations. To detect changing eclipse depths, it is advantageous to have a long time baseline of observations, which can be attained by combining data from multiple surveys. We collect ground-based photometry from the Kilodegree Extremely Little Telescope and space-based photometry from the Transiting Exoplanet Survey Satellite (TESS) for seven known changing-inclination eclipsing binaries: HS Hya, RW Per, IU Aur, AH Cep, SV Gem, V685 Cen, and SS Lac. We measure eclipse depth variations and eclipse timing variations in six systems; SS Lac no longer eclipses. As of observations presented here from TESS Sector 35, eclipses are no longer visible in HS Hya (as noted in J. R. A. Davenport et al. 2021). SV Gem, previously believed to have stopped eclipsing, exhibits eclipse-like features across all years of observation, as well as evidence of the negative “O’Connell Effect.” We also present high-resolution speckle imaging from Gemini-North, Gemini-South, and the NESSI instrument on the WIYN telescope for RW Per, AH Cep, SV Gem, and SS Lac, none of which revealed a third companion. Speckle imaging of IU Aur from NESSI revealed the presence of a third companion at an angular separation of ∼0 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>.</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>″</mml:mi> </mml:mrow> </mml:mover> </mml:math> 14; we report the details of this detection.