Submillimeter continuum variability in Planck Galactic cold clumps
  In the early stages of star formation, a protostar is deeply embedded in an
optically thick envelope such that it is not directly observable. Variations in
the protostellar accretion rate, however, will cause luminosity changes that
are reprocessed by the surrounding envelope and are observable at submillimeter
wavelengths. We searched for submillimeter flux variability toward 12 Planck
Galactic Cold Clumps detected by the James Clerk Maxwell Telescope
(JCMT)-SCUBA-2 Continuum Observations of Pre-protostellar Evolution (SCOPE)
survey. These observations were conducted at 850 um using the JCMT/SCUBA-2.
Each field was observed three times over about 14 months between 2016 April and
2017 June. We applied a relative flux calibration and achieved a calibration
uncertainty of ~ 3.6% on average. We identified 136 clumps across 12 fields and
detected four sources with flux variations of ~ 30%. For three of these
sources, the variations appear to be primarily due to large-scale
contamination, leaving one plausible candidate. The flux change of the
candidate may be associated with low- or intermediate-mass star formation
assuming a distance of 1.5 kpc, although we cannot completely rule out the
possibility that it is a random deviation. Further studies with dedicated
monitoring would provide a better understanding of the detailed relationship
between submillimeter flux and accretion rate variabilities while enhancing the
search for variability in star-forming clumps farther away than the Gould Belt.
