Observational probe into evolution of Compact Hierarchical Triples

Compact Hierarchical Triples (CHTs) are systems in which the tertiary star orbits the inner binary in an orbit shorter than 1000 days. These systems were previously thought to be rare but with photometric observations from space telescopes (Kepler and TESS), we have found a few hundred new candidates. CHTs provide an interesting setup to study star formation (using orbital architecture and metallicity distribution) at small scales (less than 5 AU) and also evolution scenarios of dynamical mergers. CHTs with an eclipsing binary as the inner binary gives us an opportunity to extract information about all three stars. Further, the effects of the tertiary (e.g. eclipse depth variation) are visible in the photometric observations spanning the time frame of a present-day photometric mission. In our poster, we use TESS lightcurves and time-series spectroscopic observations to extract stellar, orbital, and atmospheric parameters of the stars in our sample of low-mass CHTs. Using this set of parameters, coupled with evolutionary tracks and numerical integrators, we probe into the stellar and dynamical evolution of a few sample CHTs. We also discuss specific evolutionary scenarios where an old CHT (~3Gyr) evolves into a contact binary with the tertiary star affecting the timescale of this evolution. The launch of PLATO will extend the timeline of observations of the CHTs and will allow us to constrain the long-term dynamical effects of these triples better.