Identification of emission-line stars in transition phase from pre-main sequence to main sequence

TL;DR

This study identifies and characterizes rare stars in the transition phase from pre-main sequence to main sequence, using photometric analysis and machine learning to understand their properties and evolutionary status.

Contribution

It introduces a method to detect transition phase stars and provides the first comprehensive analysis of their physical and rotational properties.

Findings

Identified 98 transition phase star candidates from a large sample.

Determined ages and masses of 58 candidates, revealing their evolutionary stage.

Found transition stars have intermediate rotational velocities and color excesses.

Abstract

Pre-main sequence (PMS) stars evolve into main sequence (MS) phase over a period of time. Interestingly, we found a scarcity of studies in existing literature that examines and attempts to better understand the stars in PMS to MS transition phase. The purpose of the present study is to detect such rare stars, which we named as 'Transition Phase' (TP) candidates - stars evolving from the PMS to the MS phase. We identified 98 TP candidates using photometric analysis of a sample of 2167 classical Be (CBe) and 225 Herbig Ae/Be (HAeBe) stars. This identification is done by analyzing the near- and mid-infrared excess and their location in the optical color-magnitude diagram. The age and mass of 58 of these TP candidates are determined to be between 0.1-5 Myr and 2-10.5 M$_\odot$, respectively. The TP candidates are found to possess rotational velocity and color excess values in between CBe and HAeBe stars, which is reconfirmed by generating a set of synthetic samples using the machine learning approach.