The compact triply eclipsing triple star TIC 209409435 discovered with TESS

• DOI: 10.1093/mnras/staa1817
• Publication Date: 2020-06-22T19:42:14Z
• Authors: T Borkovits; S A Rappaport; T G Tan; R Gagliano; T Jacobs; X Huang; T Mitnyan; F-J Hambsch; T Kaye; P F L Maxted; A Pál; A R Schmitt
• Keywords: Eclipse; Eccentricity (behavior); Star (game theory); Radial velocity; Spectral energy distribution; Orbit (dynamics); Triple system; Circular orbit

We report the discovery in $TESS$ Sectors 3 and 4 of a compact triply eclipsing triple star system. TIC 209409435 is previously unknown binary with period 5.717 days, presence third an outer eccentric orbit 121.872 day was found from two sets third-body eclipses eclipse timing variations. The latter exhibit signatures strong 3rd-body perturbations. After discovery, we obtained follow-up ground-based photometric observations several as well another eclipses. carried out comprehensive analyses, including simultaneous photodynamical modelling lightcurves (including both archival WASP data, our own measurements), variation curves. Also, have included fits multiple spectral energy distribution data theoretical PARSEC stellar isochrones. find that inner consists near twin stars mass 0.90 $M_\odot$ radius 0.88 $R_\odot$. just 9% more massive 18% larger radius. has rather small eccentricity while $e = 0.40$. inclination angles within 0.1$^\circ$ 0.2$^\circ$ 90$^\circ$, respectively. mutual angle $\lesssim 1/4^\circ$. All these results were without radial velocity observations.