AGB interlopers in YSO catalogues hunted out by NEOWISE

TL;DR

This study identifies and confirms AGB star interlopers in YSO catalogs using NEOWISE IR variability data, revealing misclassifications and providing a method to distinguish between these stellar objects.

Contribution

The paper introduces a periodogram analysis approach to differentiate AGB stars from YSOs in IR surveys, improving classification accuracy.

Findings

85 AGB candidates identified among YSOs

SiO maser emission detected in 10 sources confirming AGB nature

Most AGB candidates have IR colors similar to O-rich AGBs

Abstract

AGBs and YSOs often share the same domains in IR color-magnitude or color-color diagrams leading to potential mis-classification. We extracted a list of AGB interlopers from the published YSO catalogues using the periodogram analysis on NEOWISE time series data. YSO IR variability is typically stochastic and linked to episodic mass accretion. Furthermore, most variable YSOs are at an early evolutionary stage, with significant surrounding envelope and/or disk material. In contrast, AGBs are often identified by a well defined sinusoidal variability with periods of a few hundreds days. From our periodogram analysis of all known low mass YSOs in the Gould Belt, we find 85 AGB candidates, out of which 62 were previously classified as late-stage Class III YSOs. Most of these new AGB candidates have similar IR colors to O-rich AGBs. We observed 73 of these AGB candidates in the H2O, CH3OH and SiO maser lines to further reveal their nature. The SiO maser emission was detected in 10 sources, confirming them as AGBs since low mass YSOs, especially Class III YSOs, do not show such maser emission. The H2O and CH3OH maser lines were detected in none of our targets.