Dissecting the different components of the modest accretion bursts of the very young protostar HOPS 373

• Published in: arXiv.org 2022-02
• Main Authors: Sung-Yong, Yoon, Herczeg, Gregory J, Jeong-Eun, Lee, Ho-Gyu, Lee, Johnstone, Doug, Watson Varricatt, Tobin, John J, Carlos Contreras Peña, Mairs, Steve, Hodapp, Klaus, Manoj, P, Osorio, Mayra, Megeath, S Thomas, the JCMT Transient Team
• Format: Article
• Language: English
• Subjects: Brightness; Carbon monoxide; Decay; Deposition; Emission; Outflow; Protostars; Variability
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2202.05608

Observed changes in protostellar brightness can be complicated to interpret. In our JCMT~Transient monitoring survey, we discovered that a young binary protostar, HOPS 373, is undergoing a modest \(30\%\) brightness increase at 850 \(\mu\)m, caused by a factor of 1.8\(-\)3.3 enhancement in the accretion rate. The initial burst occurred over a few months, with a sharp rise and then shallower decay. A second rise occurred soon after the decay, and the source is still bright one year later. The mid-IR emission, the small-scale CO outflow mapped with ALMA, and the location of variable maser emission indicate that the variability is associated with the SW component. The near-infrared and NEOWISE \(W1\) and \(W2\) emission is located along the blueshifted CO outflow, spatially offset by \(\sim3\) to \(4^{\prime\prime}\) from the SW component. The \(K\)-band emission imaged by UKIRT shows a compact H\(_2\) emission source at the edge of the outflow, with a tail tracing the outflow back to the source. The \(W1\) emission, likely dominated by scattered light, brightens by 0.7 mag, consistent with expectations based on the sub-mm lightcurve. The signal of continuum variability in \(K\)-band and \(W2\) is masked by stable H\(_2\) emission, as seen in our Gemini/GNIRS spectrum, and perhaps by CO emission. These differences in emission sources complicate infrared searches for variability of the youngest protostars.