Accretion rates in hierarchical triple systems with discs

Abstract

Young multiple systems accrete most of their final mass in the first few Myr of their lifetime, during the protostellar and protoplanetary phases. Previous studies showed that in binary systems the majority of the accreted mass falls onto the lighter star, thus evolving to mass equalisation. However, young stellar systems often comprise more than two stars, which are expected to be in hierarchical configurations. Despite its astrophysical relevance, differential accretion in hierarchical systems remains to be understood. In this work, we investigate whether the accretion trends expected in binaries are valid for higher order multiples. We performed a set of 3D Smoothed Particle Hydrodynamics simulations of binaries and of hierarchical triples (HTs) embedded in an accretion disc, with the code Phantom. We identify for the first time accretion trends in HTs and their deviations compared to binaries. These deviations, due to the interaction of the small binary with the infalling material from the circum-triple disc, can be described with a semi-analytical prescription. Generally, the smaller binary of a HT accretes more mass than a single star of the same mass as the smaller binary. We found that in a HT, if the small binary is heavier than the third body, the standard differential accretion scenario (whereby the secondary accretes more of the mass) is hampered. Reciprocally, if the small binary is lighter than the third body, the standard differential accretion scenario is enhanced. The peculiar differential accretion mechanism we find in HTs is expected to affect their mass ratio distribution.

Accepted for publication in MNRAS, 15 pages, 13 figures, 1 tables, 2 appendices

References in corpus (13)

• Array Programming with NumPy
• SPLASH: An interactive visualisation tool for Smoothed Particle Hydrodynamics simulations
• On the diversity and statistical properties of protostellar discs
• Circumbinary Accretion from Finite and Infinite Disks
• The Evolution of the Multiplicity of Embedded Protostars II: Binary Separation Distribution & Analysis
• Gas flow and accretion via spiral streamers and circumstellar disks in a young binary protostar
• Precession and accretion in circumbinary discs: The case of HD 104237
• Gap, shadows, spirals, streamers: SPHERE observations of binary-disk interactions in GG Tau A
• GW Ori: Interactions Between a Triple-star System and its Circumtriple Disk in Action
• GG Tau: the fifth element
• Multiplicity in Early Stellar Evolution
• The evolution of the mass ratio of accreting binaries: the role of gas temperature
• Kinematic Analysis of a Protostellar Multiple System: Measuring the Protostar Masses and Assessing Gravitational Instability in the Disks of L1448 IRS3B and L1448 IRS3A

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