2019MNRAS.487.1886C

We present an extensive optical-ultraviolet photometry and analysis of a series of optical spectra of type Ia supernovae SN 2009ig and SN 2012cg. The observations range from -15 to +185 d for SN 2009ig and from -14 to 316 d for SN 2012cg, with respect to maximum light in B band. Both SN 2009ig and SN 2012cg exhibit similar properties. They have similar decline rate parameter (Δm₁₅(B)_true = 0.92 ± 0.04 for SN 2009ig and 0.93 ± 0.06 for SN 2012cg) and B band peak absolute magnitude (-19.45 ± 0.40 mag for SN 2009ig and -19.50 ± 0.31 mag for SN 2012cg). Their early spectra show high-velocity features in Si II and Ca II lines. The strong Fe III, Si III, and weak Si II λ5972 line during pre-maximum phase are indicative of hot photosphere. The post-maximum velocity evolution shows a plateau like phase with velocities ∼13 000 km s^–1 for SN 2009ig and ∼10 000 km s^–1 for SN 2012cg. Both events show spectral evolution similar to normal SNe Ia and fall in LVG and Core Normal subgroup. Both have smaller strength ratio [ R(Si II) = 0.17 for SN 2009ig and 0.20 for SN 2012cg] consistent with smaller Δm₁₅(B). Peak bolometric luminosities (logL_bol^max) of these events are estimated as 43.17 ± 0.16 and 43.24 ± 0.11 erg s^–1 suggesting that 0.60 ± 0.20 M_☉ of ⁵⁶Ni was synthesized in the explosion of SN 2009ig and 0.72 ± 0.31 M_☉ in SN 2012cg.