Planet formation in stellar binaries: Global simulations of planetesimal growth

Abstract

Planet formation around one component of a tight, eccentric binary system such as $\gamma$ Cephei (with semimajor axis around 20 AU) is theoretically challenging because of destructive high-velocity collisions between planetesimals. Despite this fragmentation barrier, planets are known to exist in such orbital configurations. Here we present a novel numerical framework for carrying out multi-annulus coagulation-fragmentation calculations of planetesimal growth, which fully accounts for the specifics of planetesimal dynamics in binaries, details of planetesimal collision outcomes, and the radial transport of solids in the disk due to the gas drag-driven inspiral. Our dynamical inputs properly incorporate the gravitational effects of both the eccentric stellar companion and the massive non-axisymmetric protoplanetary disk in which planetesimals reside, as well as gas drag. We identify a set of disk parameters that lead to successful planetesimal growth in systems such as $\gamma$ Cephei or $\alpha$ Centauri starting from $1-10$ km size objects. We identify the apsidal alignment of a protoplanetary disk with the binary orbit as one of the critical conditions for successful planetesimal growth: It naturally leads to the emergence of a dynamically quiet location in the disk (as long as the disk eccentricity is of order several percent), where favorable conditions for planetesimal growth exist. Accounting for the gravitational effect of a protoplanetary disk plays a key role in arriving at this conclusion, in agreement with our previous results. These findings lend support to the streaming instability as the mechanism of planetesimal formation. They provide important insights for theories of planet formation around both binary and single stars, as well as for the hydrodynamic simulations of protoplanetary disks in binaries (for which we identify a set of key diagnostics to verify).

Accepted to A&A

References in corpus (16)

• Initial mass function of planetesimals formed by the streaming instability
• Steady-State Size Distributions for Collisional Populations: Analytical Solution with Size-Dependent Strength
• Relative velocities among accreting planetesimals in binary systems: the circumprimary case
• Planetesimal and gas dynamics in binaries
• Planet Formation in Binary Stars: The case of Gamma Cephei
• Planet formation in Alpha Centauri A revisited: not so accretion-friendly after all
• Planet formation in stellar binaries II: overcoming the fragmentation barrier in alpha Centauri and gamma Cephei-like systems
• Planet formation in stellar binaries I: planetesimal dynamics in massive protoplanetary disks
• Planet formation in the habitable zone of alpha Centauri B
• Gap Clearing by Planets in a Collisional Debris Disk
• On the planetary interpretation of multiple gaps and rings in protoplanetary disks seen by ALMA
• Planets in Binaries: Formation and Dynamical Evolution
• Formation of Gaps in Self-Gravitating Debris Disks by Secular Resonance in a Single-planet System I: A Simplified Model
• The Effect of Binarity on Circumstellar Disk Evolution
• Evolution of $\alpha$ Centauri B's protoplanetary disc
• Debris discs in binaries: morphology and photometric signatures

Cited by in corpus (14)

• Dust Traffic Jams in Inclined Circumbinary Protoplanetary Discs I. Morphology and Formation Theory
• A complete census of planet-hosting binaries
• OGLE-2019-BLG-1470LABc: Another Microlensing Giant Planet in a Binary System?
• Formation of polar circumstellar discs in binary star systems
• Forced Eccentricity in Circumbinary Discs
• Chasing extreme planetary architectures: I- HD196885Ab, a super-Jupiter dancing with two stars?
• Milankovitch Cycles for a Circumstellar Earth-analog within $\alpha$ Centauri-like Binaries
• An imaged 15Mjup companion within a hierarchical quadruple system
• Formation of inner planets in the presence of a Cold Jupiter: orbital evolution and relative velocities of planetesimals
• Planetesimal Dynamics in the Presence of a Giant Planet II: Dependence on Planet Mass and Eccentricity
• Dynamical Architectures of S-type Transiting Planets in Binaries II: A Dichotomy in Orbital Alignment of Small Planets in Close Binary Systems
• The PAIRS project: a global formation model for planets in binaries. II. Gravitational perturbation effects from secondary stars
• The SPHERE view of multiple star formation
• Stellar Multiplicity in Open Clusters: Investigating Binary Fractions and Their Relationship with Cluster Properties