Photometric observations of SN 2024igg

We present and analyze photometric and spectroscopic observations of the Type Ia supernova (SN Ia) 2024igg, another super-Chandrasekhar (or 03fg-like) SN whose strong CII{lambda}6580 feature was initially misidentified as H{alpha}, thereby constraining its progenitor system, explosion parameters, and physical scenario. We conducted a comparative analysis of SN 2024igg and other 03fg-like SNe. The radiative-transfer code TARDIS was run to identify the features in the first spectrum at t~-13.9 days.

A pseudo-bolometric light curve was constructed using ultraviolet and optical photometry and was then modeled with fitting tools. SN 2024igg shows many characteristics in common with other 03fg-like objects, such as high ultraviolet flux, slowly declining light curves ({DELTA}m_15_(B)=0.90+/-0.08mag), low expansion velocities, and strong and persistent CII absorption. On the other hand, it exhibits some remarkable properties within this subgroup, including a moderately low optical luminosity (Mmax(B)=-18.99+/-0.15mag), a rise time shorter than 18.5 days, and the strongest CII{lambda}6580 ever detected.