We present the detection of day-timescale periodic variability in the r -band lightcurve of newly outbursting FU Orionis-type object HBC 722 , taken from > 42 nights of observation with the CQUEAN instrument on the McDonald Observatory 2.1m telescope .
The optical/near-IR lightcurve of HBC 722 shows a complex array of periodic variability , clustering around 5.8 day ( 0.044 mag amplitude ) and 1.28 day ( 0.016 mag amplitude ) periods , after removal of overall baseline variation .
We attribute the unusual number of comparable strength signals to a phenomenon related to the temporary increase in accretion rate associated with FUors .
We consider semi-random “ flickering ” , magnetic braking/field compression and rotational asymmetries in the disk instability region as potential sources of variability .
Assuming the 5.8 day period is due to stellar rotation and the 1.28 day period is indicative of Keplerian rotation at the inner radius of the accretion disk ( at 2 R _ { \star } ) , we derive a B-field strength of 2.2-2.7 kG , slightly larger than typical T Tauri stars .
If instead the 5.8 day signal is from a disk asymmetry , the instability region has an outer radius of 5.4 R _ { \star } , consistent with models of FUor disks .
Further exploration of the time domain in this complicated source and related objects will be key to understanding accretion processes .