(Proposal ID) S17B-022

(PI) Tanaka, Masaomi

(Proposal Title)
Probing the Geometry of Superluminous Supernovae

(Abstract)
In the last six years, a population of "superluminous" supernovae has been 
identified, which have absolute magnitudes in the range -21 to -23 mag. 
The discovery of these supernovae has been facilitated by the new generation 
of untargeted, wide-field optical surveys. Theories to explain their 
luminosity include magnetar spin down and circumstellar interaction. 
Numerous studies, based mostly on conventional photometry and spectroscopy, 
have so far not been conclusive. With this present proposal, we aim at probing 
the explosion geometry of superluminous supernovae to understand the origin of 
these extraordinary transients. For this purpose, we perform ToO spectropolari-
metric observations of two bright superluminous supernovae with Subaru/FOCAS. 
By this proposal, we will double the current sample of SLSNe with spectropolari-metric data. This proposal is coordinated with Public ESO Spectroscopic Survey 
of Transient Objects (PESSTO), with which intensive time series of spectra are 
obtained. By fully utilizing spectropolarimetric data combined with time 
series of spectra and theoretical models, we will understand the nature of 
superluminous supernovae and map their diversity.