(Proposal ID) S12A-571

(PI) Maeda, Keiichi

(Proposal Title)
Late-Time NIR Study of Nearby SNe Ia: Time-Sequence Approach

(Abstract)
We propose to take J, H & K-band spectra for nearby Type Ia Supernovae (SNe) 
at late phases (> 100 days after the discovery) by IRCS with LGS-AO. Our aim 
is to follow the time evolution - we have obtained NIR spectra of three SNe in 
April 2012 by IRCS/Subaru, and want to observe these objects again in May/June 
2012. The targets include SNe 2011fe (at ~270 days after the discovery, on 
May 2012), 2011iy (~150 days) and 2011jh (~160 days). Time evolution in the 
line flux and profiles provide fruitful information, but so far available for 
no SNe Ia in late phases in NIR. We will identify when the line profile is 
fixed in time. After that the line profile can be used in the kinematic study 
to derive the explosion geometry. Furthermore, spectra at different epochs 
will provide various lines for the kinematic study, following change in the 
thermal condition. The time evolution is essential to provide a strong 
conformation of ^56Ni/Co/Fe decay as a power source. This is the ultimate 
confirmation of the thermonuclear nature of the explosion, and is linked to 
the standard candle nature of SNe Ia. The time-sequence will be further 
complemented by those obtained (to be obtained) by Gemini and Magellan, 
providing the first data set for detailed NIR time sequence of SNe Ia in late 
phases.