Equilibrium rotation states of doubly synchronous binary asteroids

TL;DR

This paper investigates the equilibrium rotation states of doubly synchronous binary asteroids caused by the balance of YORP and BYORP effects, providing a mathematical framework and empirical coefficient calculations.

Contribution

It introduces a formalism for equilibrium states in binary asteroids and demonstrates their relative commonality through shape model analysis.

Findings

Equilibria occur when YORP and BYORP effects balance.

Such equilibrium states are relatively common among binary asteroids.

Mathematical formalism links coefficients to equilibrium conditions.

Abstract

A doubly synchronous binary asteroid simultaneously experiences YORP and BYORP, the former being independent of the radius of the orbit, while the latter linearly dependent on the radius. In many systems YORP and BYORP can compensate each other at some radius, causing an equilibrium state, to which other orbits converge in the course of their evolution. We derive mathematical formalism of such equilibria in terms of dimensionless YORP and BYORP coefficients. We compute YORP and BYORP coefficients for a set of photometric and radar shape models, and find equilibria to be relatively common.