Episodic High Velocity Outflows from V899 Mon: A Constraint On The Outflow Mechanisms

TL;DR

This study reports unprecedented large variations in outflow velocities from the young star V899 Mon during an outburst, providing new constraints on magnetically driven wind mechanisms through continuous monitoring.

Contribution

It presents the first detailed observation of large, rapid outflow velocity variations in V899 Mon, supporting magnetically driven polar winds as the primary outflow mechanism.

Findings

Outflow velocities vary from -722 km/s to -425 km/s.

Outflows are multi-component, clumpy, and episodic.

Outflow strength decouples from accretion rate.

Abstract

We report the detection of large variations in the outflow wind velocity from a young eruptive star, V899 Mon during its ongoing high accretion outburst phase. Such large variations in the outflow velocity (from -722 km s$^{-1}$ to -425 km s$^{-1}$) have never been reported previously in this family of objects. Our continuous monitoring of this source shows that the multi-component, clumpy, and episodic high velocity outflows are stable in the time scale of a few days, and vary over the time scale of a few weeks to months. We detect significant decoupling in the instantaneous outflow strength to accretion rate. From the comparison of various possible outflow mechanisms in magnetospheric accretion of young stellar objects, we conclude magnetically driven polar winds to be the most consistent mechanism for the outflows seen in V899 Mon. The large scale fluctuations in outflow over the short period makes V899 Mon the most ideal source to constrain various magnetohydrodynamics (MHD) simulations of magnetospheric accretion. *footnote: based on observations made with the Southern African Large Telescope (SALT)