Estefania Padilla Gonzalez - Exploring Type Ia Supernova Explosion Mechanisms

Although Type Ia supernovae (SNe Ia) are critical tools for cosmology, their progenitor systems and explosion mechanisms remain debated. The canonical model invokes a carbon–oxygen white dwarf igniting near the Chandrasekhar mass, yet double-detonation scenarios—where helium ignition on a sub-Chandrasekhar white dwarf triggers a secondary core detonation—offer a compelling alternative. I present two exceptionally rare SNe Ia whose photometric and spectroscopic properties are consistent with double-detonation predictions. These events, comprising less than 1% of all SNe Ia, nearly double the number of confirmed candidates and provide new constraints on this explosion channel. Beyond these peculiar events, I also re-examine the broader population of SNe Ia to investigate environmental dependencies in their standardized luminosities. The well-known mass step, the luminosity–host-mass correlation seen after standardization. Using optical–infrared photometry and non-parametric star-formation histories, I find that the overall trend persists but is largely driven by metallicity: low-metallicity (Z less than Z⊙) galaxies may account for most of the observed correlation. This result may suggest that chemical composition, rather than stellar mass alone, plays a central role in shaping standardized SN Ia brightness and informs both progenitor modeling and cosmological applications.