Pushing the boundaries of conventional core-collapse supernovae: The extremely energetic supernova SN2003ma

We report the discovery of a supernova (SN) with the highest apparent energy output to date and conclude that it represents an extreme example of the Type IIn subclass. The SN, which was discovered behind the Large Magellanic Cloud at z = 0.289 by the SuperMACHO microlensing survey, peaked at M _R = -21.5 mag and only declined by 2.9 mag over 4.7 years after the peak. Over this period, SN2003ma had an integrated bolometric luminosity of 4 × 10⁵¹erg, more than any other SN to date. The radiated energy is close to the limit allowed by conventional core-collapse explosions. Optical spectra reveal that SN2003ma has persistent single-peaked intermediate-width hydrogen lines, a signature of interaction between the SN and a dense circumstellar medium. The light curves show further evidence for circumstellar interaction, including a long plateau with a shape very similar to the classic SN IIn 1988Z - however, SN2003ma is 10 times more luminous at all epochs. The fast velocity measured for the intermediate-width Hα component (∼6000kms^-1) points toward an extremely energetic explosion (>10⁵²erg), which imparts a faster blast-wave speed to the post-shock material and a higher luminosity from the interaction than is observed in typical SNe IIn. Mid-infrared observations of SN2003ma suggest an infrared light echo is produced by normal interstellar dust at a distance ∼ 0.5pc from the SN.