# Dynamical origin of S-type planets in close binary stars

## TL;DR

This paper investigates how dynamical interactions in star clusters can lead to the formation of S-type planets in close binary systems, challenging existing theories and highlighting the influence of stellar encounter parameters.

## Contribution

It proposes a new formation scenario for S-type planets in close binaries through star-binary interactions in clusters, emphasizing the role of encounter parameters.

## Key findings

- Final S-type planet fraction depends on star mass ratio and initial orbital parameters.
- Dynamical interactions can deliver planets into close binary systems.
- Upcoming missions may provide observational evidence for this formation pathway.

## Abstract

Understanding the origin of planets that have formed in binary stars is fundamental to constrain theories of binary and planet formation. The planet occurrence rate in binaries with a separation $\lesssim 50$ AU is only $\sim$ one third that of wider binaries or single stars. This may indicate that a close companion has a ruinous influence on planet formation, because it can truncate the protoplanetary disc and pump up planetesimals eccentricity and collision probability. Nevertheless, observations have revealed a few of these systems, which challenge current planet formation theories. Dynamical interactions can deliver planets into S-type orbits. In this paper, we consider as a possible scenario for forming S-type planets in close binaries the single star-binary star interactions that commonly take place in star clusters. We find that the final fraction and orbital properties of S-type planets in close binaries are mainly determined by the mass ratio of the stars involved in the close encounter, and the initial binary and planet semi-major axes. Present and upcoming missions, as TESS, PLATO and CHEOPS may shed new light on the origin of S-type planets in close binaries.