ALMA Studies of Eruptive stars

ALMA opened a new regime for studying episodic accretion in FU/EX Ori objects. Despite becoming highly popular in the last 15 years, we are still trying to understand episodic accretion, a process relevant to forming lowmass stars, binaries, and planets. Gravitational and thermal instabilities, disk fragmentation, forming planets, and stellar encounters are some of the different proposed triggering mechanisms for the outbursts. From recent ALMA and JVLA results, it is becoming clear that the highest resolutions are needed to image the very compact disks surrounding these objects and map the instabilities driving the activity. By imaging the inner regions, we can fit the temperatures and masses to estimate Toomre’s Q and check for the conditions to cause instabilities. Here we show our attempts to understand these disks with today’s ALMA capabilities. Still, very high-resolution imaging at lower frequencies (ALMA Band 1 and the ngVLA) will allow us to measure and correct for non-thermal contribution from the disk winds, which is crucial for estimating the disk temperatures in the optically thick bands. We also present ALMA images of FU Ori, the eruptive class prototype, for the first time, mapping its physical structure and kinematics from thousands of AU to a few AU scales.