# WISE Discovery of Mid-infrared Variability in Massive Young Stellar Objects

## TL;DR

This study analyzes nine years of mid-infrared variability in approximately 800 massive young stellar objects, identifying five variable candidates and revealing diverse light curve behaviors, including a notable 690-day periodicity in one source, G335.

## Contribution

First systematic investigation of long-term MIR variability in a large, uniform sample of MYSOs, revealing diverse variability patterns and a rare periodicity in G335.

## Key findings

- Identified 5 MIR-variable MYSO candidates.
- Discovered a 690-day periodicity in G335.
- Observed 'bluer when brighter' variability trend.

## Abstract

We systematically investigate the mid-infrared (MIR; $\lambda>3 ~\mu$m) time variability of uniformly selected $\sim800$ massive young stellar objects (MYSOs) from the Red MSX Source (RMS) survey. Out of the 806 sources, we obtain reliable 9-year-long MIR magnitude variability data of 331 sources at the 3.4~$\mu$m (W1) and 4.6~$\mu$m (W2) bands by cross-matching the MYSO positions with ALLWISE and NEOWISE catalogs. After applying the variability selections using ALLWISE data, we identify 5 MIR-variable candidates. The light curves show various classes, with the periodic, plateau-like, and dipper features. Out of the obtained two color-magnitude diagram of W1 and W1$-$W2, one shows "bluer when brighter and redder when fainter" trends in variability, suggesting change in extinction or accretion rate. Finally, our results show that G335.9960$-$00.8532 (hereafter, G335) has a periodic light curve, with a $\approx 690$-day cycle. Spectral energy density model fitting results indicate that G335 is a relatively evolved MYSO; thus, we may be witnessing the very early stages of a hyper- or ultra-compact HII region, a key source for understanding MYSO evolution.