The Rise of the Remarkable Type IIn Supernova SN 2009ip

TL;DR

SN 2009ip transitioned from a luminous blue variable to a Type IIn supernova, exhibiting rapid early brightening and strong interaction with circumstellar material, with detailed high-cadence optical observations capturing its evolution.

Contribution

This study provides high-cadence optical light curves of SN 2009ip during its transition to a Type IIn supernova, revealing detailed phases of its brightness evolution and interaction with circumstellar medium.

Findings

Rapid early brightening of 0.5 mag in 6 hours

Transition to slower rise and plateau around Oct. 7

Luminosity exceeds most Type IIP supernovae

Abstract

Recent observations by Mauerhan et al. have shown the unprecedented transition of the previously identified luminous blue variable (and supernova impostor) SN 2009ip to a real Type IIn supernova (SN) explosion. We present high-cadence optical imaging of SN 2009ip obtained between 2012 UT Sep. 23.6 and Oct. 9.6, using 0.3-0.4 meter aperture telescopes from the Coral Towers Observatory in Cairns, Australia. The light curves show well-defined phases, including very rapid brightening early on (0.5 mag in 6 hr observed during the night of Sep. 24), a transition to a much slower rise between Sep. 25 and Sep. 28, and a plateau/peak around Oct. 7. These changes are coincident with the reported spectroscopic changes that, most likely, mark the start of a strong interaction between the fast SN ejecta and a dense circumstellar medium formed during the earlier LBV eruptions. In the 16-day observing period SN 2009ip brightened by 3.7 mag from I = 17.4 mag on Sep. 23.6 (MI = -14.2) to I = 13.7 mag (MI = -17.9) on Oct. 9.6, radiating ~2x10^49 erg in the optical wavelength range. Currently, SN 2009ip is more luminous than most Type IIP SNe and comparable to other Type IIn SNe.