We present ultraviolet , optical and near-infrared observations of the interacting transient SN 2009ip , covering the period from the start of the outburst in October 2012 until the end of the 2012 observing season .
The transient reached a peak magnitude of M _ { V } =-17.7 mag , and with a total integrated luminosity of 1.9 \times 10 ^ { 49 } erg over the period of August-December 2012 .
The lightcurve fades rapidly , dropping by 4.5 mag from the V band peak in 100 days .
The optical and near infrared spectra are dominated by narrow emission lines with broad electron scattering wings , signaling a dense circumstellar environment , together with multiple components of broad emission and absorption in H and He at velocities between 0.5-1.2 \times 10 ^ { 4 } km s ^ { -1 } .
We see no evidence for nucleosynthesized material in SN 2009ip , even in late-time pseudo-nebular spectra .
We set a limit of < 0.02 M _ { \odot } Â on the mass of any possible synthesized ^ { 56 } Ni from the late time lightcurve .
A simple model for the narrow Balmer lines is presented , and used to derive number densities for the circumstellar medium of between \sim 10 ^ { 9 } -10 ^ { 10 } cm ^ { -3 } .
Our near-infrared data does not show any excess at longer wavelengths , and we see no other signs of dust formation .
Our last data , taken in December 2012 , shows that SN 2009ip has spectroscopically evolved to something quite similar to its appearance in late 2009 , albeit with higher velocities .
It is possible that neither of the eruptive and high luminosity events of SN2009ip were induced by a core-collapse .
We show that the peak and total integrated luminosity can be due to the efficient conversion of kinetic energy from colliding ejecta , and that around 0.05-0.1 M _ { \odot } Â of material moving at 0.5-1 \times 10 ^ { 4 } km s ^ { -1 } could comfortably produce the observed luminosity .
The ejection of multiple shells , lack of evidence for nucleosynthesied elements and broad nebular lines , are all consistent with the pulsational-pair instability scenario .
In this case the progenitor star may still exist , and will be observed after the current outburst fades .
The long term monitoring of SN 2009ip , due its proximity , has given the most extensive data set yet gathered of a high luminosity interacting transient and its progenitor .
It is possible that purported Type IIn SNe are in fact analogues of the 2012b event and that pre-explosion outbursts have gone undetected .