Constraints on Shallow ^(56)Ni from the Early Light Curves of Type Ia Supernovae

摘要: Ongoing transient surveys are presenting an unprecedented account of the rising light curves Type Ia supernovae (SNe Ia). This early emission probes shallowest layers exploding white dwarf (WD), which can provide constraints on progenitor star and properties explosive burning. We use semianalytic models radioactively powered to analyze these observations. As we have summarized in previous work, main limiting factor determining surface distribution ^(56)Ni is lack unambiguously identified time explosion, as would be provided by detection shock breakout or shock-heated cooling. Without this SN may principle exhibit a "dark phase" for few hours days, where only from cooling that too dim detected. show assuming theoretically motivated time-dependent velocity evolution, explosion better constrained, albeit with potential systematic uncertainties. technique used infer distributions three recent SNe were caught especially their rise. In all find fairly similar distributions. Observations 2011fe 2012cg probe shallower depths than 2009ig, two cases 56Ni present merely ~10^(–2) M_☉ WDs' surfaces. The uncertainty result up order magnitude given difficulty precisely constraining time. also our conclusions about times reassess radius 2011fe, well discuss roughly t^2 power law inferred many observed curves.