Program: GN-2016A-Q-5

A shock breakout (SBO) is the brightest phenomenon in a core-collapse supernova. We have started SBO surveys with HSC from the S14A semester. Our S14A-191, S14B-048, and S14B-061 observations detected ~20 SBO candidates and had confirmed the high-z nature of 6 objects (z>0.5), and our first paper on an SBO was submitted. However, the previous single-epoch follow-up observation at ~1 month later could not reveal their evolution nor detect supernova features. Thus, it is required to obtain multicolor light curves and spectra continuously from the SBO to the plateau. We propose 2-continuous-night HSC imaging observations in the g band and immediate and continuous follow-up imaging and spectroscopic observations with GMOS, optimizing for relatively low-z SBOs (z<0.3). One of co-investigators also proposes a 1-night Keck/LRIS coordinated observation via the California Institute of Technology to make maximal use of the HSC observation. Although we had proposed similar observations in 2015, the FOCAS observation was cancelled (S15A-092), and the HSC observation was performed only for ~3 hours with poor seeing (~1.4 arcsec, S15B-033). The unprecedented observational data over ~2 months comprehensively test theoretical models from the SBO to the plateau.