# Accretion rates in hierarchical triple systems with discs

**Authors:** Simone Ceppi, Nicolás Cuello, Giuseppe Lodato, Cathie Clarke, Claudia Toci, Daniel J. Price  
**arXiv:** [2205.08784](https://arxiv.org/abs/2205.08784)  
**Date:** 2022-05-18  
**Summary page:** https://www.summarizepaper.com/en/paper/2205.08784v1/

## Key points

- Young multiple stellar systems accrete most of their final mass during the protostellar and protoplanetary phases
- Little is known about differential accretion in hierarchical systems
- A team of researchers investigated whether the accretion trends expected in binaries are valid for higher order multiples
- The team performed a set of 3D Smoothed Particle Hydrodynamics simulations using the code Phantom to investigate how hierarchical triples (HTs) embedded in an accretion disc differ from binary systems
- Smaller binaries within HTs tend to accrete more mass than single stars of equivalent mass, but if the small binary is heavier than the third body within an HT system, then standard differential accretion scenarios are hampered; conversely, if it is lighter than its third body counterpart, then standard differential accretion scenarios are enhanced.
- The peculiar differential accretion mechanism observed by this research team in HTs is expected to affect their mass ratio distribution.
- This study sheds light on differential accretion mechanisms within hierarchical multiple stellar systems and provides new insights into how these mechanisms impact overall system evolution.

## Summary

In the early stages of their lifetime, young multiple stellar systems accrete most of their final mass during the protostellar and protoplanetary phases. While previous studies have shown that in binary systems, the majority of the accreted mass falls onto the lighter star, leading to mass equalisation, little is known about differential accretion in hierarchical systems. In this study, published in MNRAS, a team of researchers investigated whether the accretion trends expected in binaries are valid for higher order multiples. The team performed a set of 3D Smoothed Particle Hydrodynamics simulations using the code Phantom to investigate how hierarchical triples (HTs) embedded in an accretion disc differ from binary systems. They identified for the first time accretion trends in HTs and their deviations compared to binaries. These deviations were due to the interaction of the small binary with infalling material from the circum-triple disc and could be described with a semi-analytical prescription. The team found that generally, smaller binaries within HTs tend to accrete more mass than single stars of equivalent mass. However, if the small binary is heavier than the third body within an HT system, then standard differential accretion scenarios are hampered. Conversely, if it is lighter than its third body counterpart, then standard differential accretion scenarios are enhanced. The peculiar differential accretion mechanism observed by this research team in HTs is expected to affect their mass ratio distribution. The study also discusses how these findings could help reveal unresolved hierarchical triple systems from their accretion rates but highlights difficulties in constraining orbital parameters for unresolved small binaries. Overall, this study sheds light on differential accretion mechanisms within hierarchical multiple stellar systems and provides new insights into how these mechanisms impact overall system evolution.