Accretion Variability of Hα in Transitional Disk Host-Stars: Constraints on Second-to-Minute Hɑ Variability from the Giant Accreting Protoplanet Survey

The accretion process is the defining characteristic of young stellar objects (YSOs). The process by which stars accrete their circumstellar disks is that of magnetospheric accretion—in which the magnetic field truncates the inner disk material along field lines, and crashes on to the photosphere. Models and observations of YSOs undergoing accretion have shown that the in-flow of material produces an excess of Hα emission, which has caused the atomic line to become a popular tracer of accretion. Accretion onto the central star and onto protoplanets embedded within the disk are thought to carve out large gaps (~10-100’s of AU) between the central star and disk, creating the subset of objects known as transitional disks. While accretion in transitional disks is not well-understood on theoretical grounds, observations have shown that these objects are still actively accreting despite their large cavities. In fact, no significant differences in accretion between transitional and full disks have been found to date. This is a surprising fact since the large cavities in between the central star and the outer disks of transitional objects would immediately suggest otherwise. Accretion studies on YSOs with transitional disks are far and few, and time-domain studies are even scarcer. As a result, we have a limited understanding of the timescales of accretion variability in transitional disk systems. This project seeks to inform the conversation of accretion variability in transitional systems by producing light-curves for 15 of the most well-studied transitional disk bearing stars (GAPlanetS Survey). We then perform a time-series analysis to search for and constrain variability due to changes in accretion rate on second-minute timescales over the course of 5 years.