2025ApJ...978..112W

In this study, we perform detailed spectroscopic modeling to analyze the interaction of circumstellar material (CSM) with ejecta in both hydrogen-rich and hydrogen-poor superluminous supernovae (SLSNe), by systematically varying properties such as the CSM density, composition, and geometry to explore their effects on spectral lines and light-curve evolution. Using advanced radiative transfer simulations with the new, open-source SuperLite code to generate synthetic spectra, we identify key spectroscopic indicators of CSM characteristics. Our findings demonstrate that spectral lines of hydrogen and helium exhibit significant variations due to differences in CSM mass and composition. In hydrogen-rich Type II SLSNe, we observe pronounced hydrogen emission lines that correlate strongly with a dense, extended CSM, suggesting massive, eruptive mass-loss histories. Conversely, in hydrogen-poor SLSNe, we recover mostly featureless spectra at early times, with weak hydrogen lines appearing only in the very early phases of the explosion, highlighting the quick ionization of traces of hydrogen present in the CSM. We analyze the properties of the resulting emission lines, particularly H_α and H_β, for our models using sophisticated statistical methods. This analysis reveals how variations in the SN progenitor and CSM properties can lead to distinct spectroscopic evolutions over time. These temporal changes provide crucial insights into the underlying physics driving the explosion and the subsequent interaction with the CSM. By linking these spectroscopic observations to the initial properties of the progenitor and its surrounding material, our study offers a useful tool for probing the pre-explosion histories of these explosive events.