Program: GN-2013A-Q-3

We propose to establish the newly discovered unusually long (a few 100 days) and luminous (absolute magnitude of -20) optical transient (e.g. SDF-05M05) as the new type of astrophysical object. The duration of the transient is significantly longer than the ultra-luminous supernova (ULSNe). Although we cannot entirely rule out the possibility of this event being of peculiar SNIIn because of lack of optical spectrum, the transient may be a new type of optical transient altogether. Because broadband SED are different with those of SNIIn and the temperature is also significantly lower. Pan-STARRS1 is very powerful to find out these transients thanks to their deep surveys for the Medium Deep Survey fields. However, the lack of spectroscopic follow-ups (especially for apparently faint transients) makes it difficult to identify their type and estimate their absolute magnitudes. Here, we aim to establish the SDF-05M05 type as the new class of transient with identifying their spectral type and estimate absolute magnitude with Gemini/GMOS under the standard ToO mode. This establishment will enrich the studies of interstellar medium in distant galaxies as same as the ULSNe case. But the SDF-05M05 type will be much more steady light source because of their longer lifetime.