A Study of Millimeter Variability in FUor Objects
  FU Orionis objects (FUors) are rapidly-accreting, pre-main sequence objects
that are known to exhibit large outbursts at optical and near-infrared
wavelengths, with post-eruption, small-scale photometric variability
superimposed on longer-term trends. In contrast, little is known about the
variability of FUors at longer wavelengths. To explore this further, we
observed six FUor objects using the NOrthern Extended Millimeter Array (NOEMA)
and for a subset of three objects we obtained coordinated observations with
NOEMA and the Lowell Discovery Telescope (LDT). In combination with previously
published NOEMA observations from 2014, our 2017 observations of V1735 Cyg
provide the first detection of variability in an FUor object at 2.7 mm. In the
absence of significant optical variability, we discount the possibility that
the mm flux density changed as a result of irradiation from the central disk.
In addition, a change in the dust mass due to infall is highly unlikely. A
plausible explanation for the change in 2.7 mm flux density is variability in
free-free emission due to changes in the object's jet/wind. Thus, it may be
that free-free emission in some FUor objects is significant at $\sim$3 mm and
must be considered when deriving disk masses in order to help constrain the
mechanism responsible for triggering FUor outbursts.
