Evidence for Rapid Variability in the Optical Light Curve of the Type Ia SN 2014J

We present results of high-cadence monitoring of the optical light curve of the nearby, Type Ia SN 2014J in M82 using the 2.3m Aristarchos telescope. $B$ and $V$-band photometry on days 15-18 after $t_{max}(B)$, obtained with a cadence of 2 min per band, reveals evidence for rapid variability at the 0.02-0.05 mag level on timescales of 15-60 min on all four nights, taking the red noise estimation at face value. The decline slope was measured to be steeper in the $B$-band than in $V$-band, and to steadily decrease in both bands from 0.15 mag/day (night 1) to 0.04 mag/day (night 4) in V and from 0.19 mag/day (night 1) to 0.06 mag/day (night 4) in B, corresponding to the onset of the secondary maximum. We propose that rapid variability could be due to one or a combination of the following scenarios: the clumpiness of the ejecta, their interaction with circumstellar material, the asymmetry of the explosion, or the mechanism causing the secondary maximum in the near-infrared light curve. We encourage the community to undertake high-cadence monitoring of future, nearby and bright supernovae to investigate the intraday behavior of their light curves.