A Study of Millimeter Variability in FUor Objects

FUor objects (a class of outbursting, young, pre-main sequence stars) have been shown to be variable at millimeter wavelengths on timescale of ~years. We find that the object V1735 Cyg exhibited a ~80% increase in 2.7 mm flux between 2014 and 2017. It does not show corresponding variability at optical/NIR wavelengths, but shows a decrease in the millimeter spectral index. This implies that the mllimeter flux increase may be due to an accretion event which increased the contribution from free-free emission in the jet. This result shows that an FUor disk mass obtained from millimeter flux may be overestimated if the object has recently undergone recent accretion activity.