How eclipse time variations, eclipse duration variations, and radial velocities can reveal S-type planets in close eclipsing binaries

TL;DR

This paper introduces a new method combining radial velocities, eclipse timing, and duration variations to detect S-type planets in eclipsing binaries, demonstrating its effectiveness through simulations and potential for orbit characterization.

Contribution

The study proposes a novel detection technique for S-type planets in eclipsing binaries using RV, ETV, and EDV correlations, validated by simulations and applicable with current instruments.

Findings

The method can distinguish prograde and retrograde orbits.

Planetary mass can be estimated from RV-ETV diagrams.

S-type planets contribute minimally to the Rossiter-McLaughlin effect.

Abstract

While about a dozen transiting planets have been found in wide orbits around an inner, close stellar binary (so-called "P-type planets"), no planet has yet been detected orbiting only one star (a so-called "S-type planet") in an eclipsing binary. This is despite a large number of eclipsing binary systems discovered with the Kepler telescope. Here we propose a new detection method for these S-type planets, which uses a correlation between the stellar radial velocities (RVs), eclipse timing variations (ETVs), and eclipse duration variations (EDVs). We test the capability of this technique by simulating a realistic benchmark system and demonstrate its detectability with existing high-accuracy RV and photometry instruments. We illustrate that, with a small number of RV observations, the RV-ETV diagrams allows us to distinguish between prograde and retrograde planetary orbits and also the planetary mass can be estimated if the stellar cross-correlation functions can be disentangled. We also identify a new (though minimal) contribution of S-type planets to the Rossiter-McLaughlin effect in eclipsing stellar binaries. We finally explore possible detection of exomoons around transiting luminous giant planets and find that the precision required to detect moons in the RV curves of their host planets is of the order of ${\rm cm\,s}^{-1}$ and therefore not accessible with current instruments.