Understanding Episodic Accretion and Outflows in Young Stellar Objects

Protoplanetary discs are the nurseries of planets and comets which form systems like our own solar system. They are also the channel through which young low mass stars accumulate their final mass during the pre-main sequence phase of their life. Recent observations and some observational paradoxes have strongly hinted at an episodic nature to the accretion of matter from the protoplanetary disc to the central young star.  In this talk, I shall start with a brief outline of the motivations for the episodic accretion hypothesis, and its implications on planet formation.


The physical mechanism which drives these episodic accretion outbursts is poorly understood. I shall present the constraints we deduced on possible physical mechanisms from our detailed study of two eruptive young stellar objects (YSOs), using data from our long-term multi-wavelength Monitoring of FUors and EXors (MFES) program. The large variations in the accretion rate of these sources within short time-scales, make them ideal laboratories to test accretion-outflow relationships. I shall present possibly the first detection of magnetically-driven polar winds in these objects. Recognizing the importance of constraining how frequently these accretion outbursts occur across the lifetime of a protoplanetary disc, we developed a simple hierarchical Bayesian model, which enables us for the first time, to do comparisons across different age classes of YSOs.


I shall conclude the talk, by briefly outlining some of the future works I plan to undertake in order to further understand the outflow-accretion relationship as well as their effects on the planet formation environment.