Multi-wavelength Optical and NIR Variability Analysis of the Blazar PKS
  0027-426
  We present multi-wavelength spectral and temporal variability analysis of PKS
0027-426 using optical griz observations from DES (Dark Energy Survey) between
2013-2018 and VOILETTE (VEILS Optical Light curves of Extragalactic TransienT
Events) between 2018-2019 and near infrared (NIR) JKs observations from VEILS
(VISTAExtragalactic Infrared Legacy Survey) between 2017-2019. Multiple methods
of cross-correlation of each combination of light curve provides measurements
of possible lags between optical-optical, optical-NIR, and NIR-NIR emission,
for each observation season and for the entire observational period. Inter-band
time lag measurements consistently suggest either simultaneous emission or
delays between emission regions on timescales smaller than the cadences of
observations. The colour-magnitude relation between each combination of filters
was also studied to determine the spectral behaviour of PKS 0027-426. Our
results demonstrate complex colour behaviour that changes between bluer when
brighter (BWB), stable when brighter (SWB) and redder when brighter (RWB)
trends over different timescales and using different combinations of optical
filters. Additional analysis of the optical spectra is performed to provide
further understanding of this complex spectral behaviour.
