The PAIRS project: a global formation model for planets in binaries. I. Effect of disc truncation on the growth of S-type planets

TL;DR

This paper introduces the PAIRS project, a model for planet formation in binary systems, focusing on how disc truncation affects the growth of S-type planets, with implications for understanding observed exoplanet populations.

Contribution

The paper adapts the Bern Model to include binary star effects, providing a new framework for simulating S-type planet formation considering disc truncation and heating.

Findings

Disc truncation significantly reduces pebble supply for planet core growth.

Planet formation is suppressed in binaries with separations below 160 au.

S-type planets tend to form close to the primary star near the truncation radius.

Abstract

Binary stars are as common as single stars. The number of detected planets orbiting binaries is rapidly increasing thanks to the synergy between transit surveys, Gaia and high-resolution direct imaging campaigns. However, global planet formation models around binary stars are still underdeveloped, which limits the theoretical understanding of planets orbiting binary star systems. Hereby we introduce the PAIRS project, which aims at building a global planet formation model for planets in binaries, and to produce planet populations synthesis to statistically compare theory and observations. In this first paper, we present the adaptation of the circumstellar disc to simulate the formation of S-type planets. The presence of a secondary star tidally truncates and heats the outer part of the circumprimary disc (and vice-versa for the circumsecondary disc), limiting the material to form planets. We implement and quantify this effect for a range of binary parameters by adapting the Bern Model of planet formation in its pebble-based form and for in-situ planet growth. We find that the disc truncation has a strong impact on reducing the pebble supply for core growth, steadily suppressing planet formation for binary separations below 160 au, when considering all the formed planets more massive than Mars. We find as well that S-type planets tend to form close to the central star with respect to the binary separation and disc truncation radius. Our newly developed model will be the basis of future S-type planet population synthesis studies.