The Burst Mode of Accretion in Primordial Protostars

TL;DR

This study uses hydrodynamic simulations to investigate how primordial protostellar disks form, fragment, and produce episodic accretion bursts, which could significantly influence early star growth and luminosity.

Contribution

It demonstrates that burst accretion phenomena are common across various initial conditions in primordial star formation, highlighting their role in protostellar evolution.

Findings

Multiple fragmentation episodes observed in disks.

Accretion bursts reach luminosities of about 10^7 solar luminosities.

Repetitive fragmentation driven by continuous mass infall.

Abstract

We study the formation and long-term evolution of primordial protostellar disks harbored by first stars using numerical hydrodynamics simulations in the thin-disk limit. The initial conditions are specified by pre-stellar cores with distinct mass, angular momentum, and temperature. This allows us to probe several tens of thousand years of the disk's initial evolution, during which we observe multiple episodes of fragmentation leading to the formation of gravitationally bound gaseous clumps within spiral arms. These fragments are torqued inward due to gravitational interaction with the spiral arms on timescales of 10^3 - 10^4 yr and accreted onto the growing protostar, giving rise to accretion and luminosity bursts. The burst phenomenon is fueled by continuing accretion of material falling onto the disk from the collapsing parent core, which replenishes the mass lost by the disk due to accretion, and triggers repetitive episodes of disk fragmentation. We show that the burst phenomenon is expected to occur for a wide spectrum of initial conditions in primordial pre-stellar cores and speculate on how the intense luminosities (~10^7 solar luminosities) produced by this mechanism may have important consequences for the disk evolution and subsequent growth of the protostar.