Light curves of hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory

Cia, AD, Gal-Yam, A, Rubin, A, Leloudas, G, Vreeswijk, P, Perley, DA, Quimby, R, Yan, L, Sullivan, M, Flörs, A, Sollerman, J, Bersier, D, Cenko, SB, Gal-Yam, M, Maguire, K, Ofek, EO, Prentice, SJ, Schulze, S, Spyromilio, J, Valenti, S , Arcavi, I, Corsi, A, Howell, A, Mazzali, PA, Kasliwal, MM, Taddia, F and Yaron, O (2018) Light curves of hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory. Astrophysical Journal, 860 (2). ISSN 0004-637X

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Light curves of hydrogen-poor Superluminous Supernovae from the Palomar Transient Factory.pdf - Accepted Version

We investigate the light-curve properties of a sample of 26 spectroscopically confirmed hydrogen-poor superluminous supernovae (SLSNe-I) in the Palomar Transient Factory (PTF) survey. These events are brighter than SNe Ib/c and SNe Ic-BL, on average by about 4 and 2 mag, respectively. The SLSNe-I peak absolute magnitudes in rest-frame $g$-band span $-22\lesssim M_g \lesssim-20$ mag, and these peaks are not powered by radioactive $^{56}$Ni, unless strong asymmetries are at play. The rise timescales are longer for SLSNe than for normal SNe Ib/c, by roughly 10 days, for events with similar decay times. Thus, SLSNe-I can be considered as a separate population based on a photometric criterion. After peak, SLSNe-I decay with a wide range of slopes, with no obvious gap between rapidly-declining and slowly-declining events. The latter events show more irregularities (bumps) in the light curves at all times. At late times the SLSN-I light curves slow down and cluster around the $^{56}$Co radioactive decay rate. Powering the late-time light curves with radioactive decay would require between 1 and 10 ${\rm M}_\odot$ of Ni masses. Alternatively, a simple magnetar model can reasonably fit the majority of SLSNe-I light curves, with three exceptions, and can mimic the radioactive decay of $^{56}$Co, up to $\sim400$ days from explosion. The resulting spin values do not correlate with the host-galaxy metallicities. Finally, the analysis of our sample cannot strengthen the case for using SLSNe-I for cosmology.