Rapidly Rising Transients in the Supernova - Superluminous Supernova Gap

摘要: We present observations of four rapidly rising (t_{rise}~10d) transients with peak luminosities between those supernovae (SNe) and superluminous SNe (M_{peak}~-20) - one discovered followed by the Palomar Transient Factory (PTF) three Supernova Legacy Survey (SNLS). The light curves resemble SN 2011kl, recently shown to be associated an ultra-long-duration gamma ray burst (GRB), though no GRB was seen accompany our SNe. rapid rise a luminous places these events in unique part phase space, challenging standard emission mechanisms. Spectra PTF event formally classify it as Type II due broad Halpha emission, but unusual absorption feature, which can interpreted either high velocity (though deeper than previously known cases) or Si (as Ia SNe), is also observed. find that existing models white dwarf detonations, CSM interaction, shock breakout wind (or steeper CSM) magnetar spindown not readily explain observations. consider possibility "Type 1.5 SN" scenario could origin events. More detailed for kinds more constraining future such should help better determine their nature.