The outburst and nature of young eruptive low mass stars in dark clouds

TL;DR

This paper reviews the significance of FUor and EXor outbursts in the early stages of low-mass star development, emphasizing the importance of long-term monitoring to understand these rare eruptive phenomena.

Contribution

It presents recent observational results from long-term monitoring of eruptive young stellar objects using Himalayan Chandra Telescope and IUCAA Girawali Observatory.

Findings

Observed three rare types of eruptive young variables.

Provided data on outburst durations and magnitudes.

Enhanced understanding of early stellar evolution processes.

Abstract

The FU Orionis (FUor) or EX Orionis (EXor) phenomenon has attracted increasing attention in recent years and is now accepted as a crucial element in the early evolution of low-mass stars. FUor and EXor eruptions of young stellar objects (YSOs) are caused by strongly enhanced accretion from the surrounding disk. FUors display optical outbursts of $\sim$ 4 mag or more and last for several decades, whereas EXors show smaller outbursts ($\Delta$m $\sim$ 2 - 3 mag) that last from a few months to a few years and may occur repeatedly. Therefore, FUor/EXor eruptions represent a rare but very important phenomenon in early stellar evolution, during which a young low-mass YSO brightens by up to several optical magnitudes. Hence, long-term observations of this class of eruptive variable are important to design theoretical models of low-mass star formation. In this paper, we present recent results from our long-term monitoring observations of three rare types of eruptive young variables with the 2-m Himalayan {\it Chandra} Telescope (HCT) and the 2-m IUCAA Girawali Observatory (IGO) telescope.