V899 Mon: An Outbursting Protostar With Peculiar Light Curve And Its Transition Phases

TL;DR

V899 Mon is a young star exhibiting complex outburst behavior with transitions between active and quiescent phases, providing insights into accretion and outflow processes in protostars.

Contribution

This study provides the first detailed long-term monitoring of V899 Mon, revealing its unique outburst and quiescence transitions and their relation to accretion and outflow dynamics.

Findings

Observed transition from outburst to quiescence and back in V899 Mon.

Resolved clumpy outflow structures with high-resolution spectroscopy.

Detected flux changes between outburst epochs.

Abstract

We present a detailed study of V899 Mon (a new member in the FUors/EXors family of young low-mass stars undergoing outburst), based on our long-term monitoring of the source starting from November 2009 to April 2015. Our optical and near-infrared photometric and spectroscopic monitoring recorded the source transitioning from its first outburst to a short duration quiescence phase ($<$ 1 year), and then returning to a second outburst. We report here the evolution of the outflows from inner region of the disk as the accretion rate evolved in various epochs. Our high resolution (R$\sim$37000) optical spectrum could resolve interesting clumpy structures in the outflow traced by various lines. Change in far-infrared flux was also detected between two outburst epochs. Based on our observations we constrained various stellar and envelope parameters of V899 Mon, as well as the kinematics of its accretion and outflow. The photometric and spectroscopic properties of this source fall between classical FUors and EXors. Our investigation of V899 Mon hints instability associated with magnetospheric accretion to be the physical cause of sudden short duration pause of outburst in 2011. It is also a good candidate to explain similar short duration pauses in outburst of some other FUors/EXors sources.