Episodic accretion: the interplay of infall and disc instabilities

TL;DR

This study uses high-resolution simulations to explore how environmental factors and disc instabilities influence protostellar accretion, luminosity, and observable signatures during early star formation stages.

Contribution

It demonstrates the impact of environment and disc instabilities on accretion bursts and protostellar properties, providing new insights into episodic accretion processes.

Findings

Environmental conditions shape accretion profiles.

Disc instabilities cause rapid accretion bursts.

Accretion bursts significantly alter protostellar luminosity and spectra.

Abstract

Using zoom-simulations carried out with the adaptive mesh-refinement code RAMSES with a dynamic range of up to $2^{27} \approx 1.34 \times 10^8$ we investigate the accretion profiles around six stars embedded in different environments inside a (40 pc)$^3$ giant molecular cloud, the role of mass infall and disc instabilities on the accretion profile, and thus on the luminosity of the forming protostar. Our results show that the environment in which the protostar is embedded determines the overall accretion profile of the protostar. Infall on to the circumstellar disc may trigger gravitational disc instabilities in the disc at distances of around ~10 to ~50 au leading to rapid transport of angular momentum and strong accretion bursts. These bursts typically last for about ~10 to a ~100 yr, consistent with typical orbital times at the location of the instability, and enhance the luminosity of the protostar. Calculations with the stellar evolution code mesa show that the accretion bursts induce significant changes in the protostellar proper- ties, such as the stellar temperature and radius. We apply the obtained protostellar properties to produce synthetic observables with RADMC3D and predict that accretion bursts lead to ob- servable enhancements around 20 to 200 $\mu$m in the spectral energy distribution of Class 0 type young stellar objects.