UC Santa Cruz

Since the beginning of the modern telescope, astronomers have thought of new surveys and methods to study astrophysical phenomena. In this dissertation, I present the Swope Supernova Survey, a low-redshift photometric survey at Las Campanas Observatory, Chile, detailing its motivation, methodology, and significant contributions to transient astrophysics. I also highlight my vital contributions to the survey and science enabled. Since its inception in 2016, the survey has established itself as a critical resource for the study of transients below +30◦ declination, covering a wide wavelength range (u to i band), precise calibration, and high observing cadences. I specifically focus on the first Type Ia Supernova (SN Ia) data release, an effort that I led to provide over 100 high-cadence light curves in five photometric bands. This dataset enhances low-redshift SN Ia samples and opens the path for future work that will significantly contribute to SN cosmology. Finally, I introduce a novel parametrization of i-band light-curve diversity. I present the ∆m1 − ∆m2 parameter, which captures differences between the data and model at the i-band secondary maximum and minimum. Strong correlations are identified between this parameter and key spectral features, such as Ca II pEW0 and Si II v0, highlighting the role of spectral variations in shaping i-band light curves. This work also shows how these variations impact SN Ia composite spectra and synthetic photometry, revealing limitations in the widely used SALT3 SN Ia model. This dissertation highlights the importance of combining photometric and spectroscopic analyses to advance our understanding of SNe Ia, further exploring connections between SN Ia spectral features, i-band light-curve morphology and diversity, physical processes, environmental dependencies, and the accuracy of SNe Ia as precise cosmological distance indicators.