High Mass Inner Regions Found in Five Outbursting Sources

TL;DR

This study measures the mass of five outbursting young stellar objects using CO emission, revealing that their inner regions contain enough mass to be gravitationally unstable, which may influence planet formation.

Contribution

It provides new mass estimates of the inner regions of outbursting sources using C17O emission, highlighting potential gravitational instability.

Findings

Inner regions contain 0.33-3.4 Msun of material.

Inner 1000 au regions are potentially gravitationally unstable.

Mass estimates suggest active accretion and planet formation processes.

Abstract

Young stellar objects are thought to commonly undergo sudden accretion events that result in a rise in bolometric luminosity. These outbursts likely coincide with the onset of planet formation, and could impact the formation of planets. The reason behind this dramatic enhancement of accretion is an active area of research, and the mass of the system is a critical parameter. Using Northern Extended Millimeter Array, we survey five outbursting sources (three FU Ori, one EX Or, one 'peculiar' source) with the primary goal of determining the system's mass using an optically thin line of CO. We estimate the mass of a central region for each object that using both continuum emission and C17O J=2-1. The C17O emission likely includes both disk and inner envelope material, thus acts as an upper limit on the disk mass, ranging from 0.33-3.4 Msun for our sources. These derived masses suggest that the inner approx. 1000 au contains enough mass along the line of sight for these sources to be gravitationally unstable.