McCrum, M.Smartt, S. J.Kotak, R.Rest, A.Jerkstrand, A.Inserra, C.Rodney, S. A.Chen, T.- W.Howell, D. A.Huber, M. E.Pastorello, A.Tonry, J. L.Bresolin, F.Kudritzki, R.- P.Chornock, R.Berger, EdoSmith, K.Botticella, M. T.Foley, R. J.Fraser, M.Milisavljevic, DannyNicholl, M.Riess, A. G.Stubbs, ChristopherValenti, S.Wood-Vasey, W. M.Wright, D.Young, D. R.Drout, Maria RebeccaCzekala, IanBurgett, W. S.Chambers, K. C.Draper, P.Flewelling, H.Hodapp, K. W.Kaiser, N.Magnier, E. A.Metcalfe, N.Price, P. A.Sweeney, W.Wainscoat, R. J.2015-08-262013McCrum, M., S. J. Smartt, R. Kotak, A. Rest, A. Jerkstrand, C. Inserra, S. A. Rodney, et al. 2013. “The Superluminous Supernova PS1-11ap: Bridging the Gap Between Low and High Redshift.” Monthly Notices of the Royal Astronomical Society 437 (1) (November 7): 656–674. doi:10.1093/mnras/stt1923.0035-8711http://nrs.harvard.edu/urn-3:HUL.InstRepos:20577462We present optical photometric and spectroscopic coverage of the superluminous supernova (SLSN) PS1-11ap, discovered with the Pan-STARRS1 Medium Deep Survey at z = 0.524. This intrinsically blue transient rose slowly to reach a peak magnitude of Mu = −21.4 mag and bolometric luminosity of 8 × 1043 erg s−1 before settling on to a relatively shallow gradient of decline. The observed decline is significantly slower than those of the SLSNe-Ic which have been the focus of much recent attention. Spectroscopic similarities with the lower redshift SN2007bi and a decline rate similar to 56Co decay time-scale initially indicated that this transient could be a candidate for a pair instability supernova (PISN) explosion. Overall the transient appears quite similar to SN2007bi and the lower redshift object PTF12dam. The extensive data set, from 30 d before peak to 230 d after, allows a detailed and quantitative comparison with published models of PISN explosions. We find that the PS1-11ap data do not match these model explosion parameters well, supporting the recent claim that these SNe are not pair instability explosions. We show that PS1-11ap has many features in common with the faster declining SLSNe-Ic, and the light-curve evolution can also be quantitatively explained by the magnetar spin-down model. At a redshift of z = 0.524, the observer-frame optical coverage provides comprehensive rest-frame UV data and allows us to compare it with the SLSNe recently found at high redshifts between z = 2 and 4. While these high-z explosions are still plausible PISN candidates, they match the photometric evolution of PS1-11ap and hence could be counterparts to this lower redshift transient.en-USJournal Article2015-08-2610.1093/mnras/stt1923