Priscila Pessi: They Look Like Type II Supernovae — But They Are Not

Thursday 5 Feb 2026, 13:15 → 14:00 Europe/Stockholm

A5:1003 (AlbaNova Main Building)

Massive stars that retain their hydrogen envelopes until the end of their lives can produce hydrogen-rich Type II supernova explosions. However, not all transients that resemble Type II supernovae arise from the same physical processes. Some energetic events can mimic Type II supernovae without being genuine stellar explosions, while others may appear hydrogen-rich based on early classifications but lack hydrogen in their spectra.

In this talk, I will present two illustrative cases. The first is a transient initially classified as a core-collapse supernova that, based on detailed observational analysis, was later identified as nuclear activity in its host galaxy. The second is an ongoing study of a supernova candidate originally classified as Type II, for which no hydrogen features are detected in the spectra. Together, these examples show how misclassification can lead to incorrect inferences about the physical mechanisms powering different transients, and they highlight the limitations of current supernova diagnostics. This work emphasizes the need for robust identification strategies to correctly interpret the physics of transients in the era of large survey data sets.