We systematically investigate the mid-infrared (MIR; λ>3μm) time variability of uniformly selected ∼800 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~μm (W1) and 4.6~μm (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 ≈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.
@article{arxiv.1907.13244,
title = {WISE Discovery of Mid-infrared Variability in Massive Young Stellar Objects},
author = {Mizuho Uchiyama and Kohei Ichikawa},
journal= {arXiv preprint arXiv:1907.13244},
year = {2019}
}