THE EXCEPTIONALLY LUMINOUS TYPE II-LINEAR SUPERNOVA 2008es

We report on our early photometric and spectroscopic observations of the\nextremely luminous Type II supernova (SN) 2008es. With an observed peak optical\nmagnitude of m_V = 17.8 and at a redshift z = 0.213, SN 2008es had a peak\nabsolute magnitude of M_V = -22.3, making it the second most luminous SN ever\nobserved. The photometric evolution of SN 2008es exhibits a fast decline rate\n(~0.042 mag d^-1), similar to the extremely luminous Type II-L SN 2005ap. We\nshow that SN 2008es spectroscopically resembles the luminous Type II-L SN\n1979C. Although the spectra of SN 2008es lack the narrow and intermediate-width\nline emission typically associated with the interaction of a SN with the\ncircumstellar medium of its progenitor star, we argue that the extreme\nluminosity of SN 2008es is powered via strong interaction with a dense,\noptically thick circumstellar medium. The integrated bolometric luminosity of\nSN 2008es yields a total radiated energy at ultraviolet and optical wavelengths\nof >10^51 ergs. Finally, we examine the apparently anomalous rate at which the\nTexas Supernova Search has discovered rare kinds of supernovae, including the\nfive most luminous supernovae observed to date, and find that their results are\nconsistent with those of other modern SN searches.\n