2015AJ....149....9M

The supernova (SN) impostor SN 2009ip has re-brightened several times since its initial discovery in 2009 August. During its last outburst in late 2012 September, it reached a peak brightness of m_v: (13.5 (M_v brighter than -18), causing some to speculate that it had undergone a terminal core-collapse SN. Relatively high-cadence multi-wavelength photometry of the post-peak decline revealed bumps in brightness infrequently observed in other SNe IIn. These bumps occurred synchronously in all ultraviolet (UV) and optical bands with amplitudes of 0.1-0.4 mag at intervals of 10-30 days. Episodic continuum brightening and dimming in the UV and optical with these characteristics is not easily explained within the context of models that have been proposed for the late September 2012 outburst of SN 2009ip. We also present evidence that the post-peak fluctuations in brightness occur at regular intervals and raise more questions about their origin.