Anjasha Gangopadhyay: A Systematic Study of Interacting Type Ibn Supernovae from the Zwicky Transient Facility

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

FB52 (AlbaNova Main Building)

Type Ibn supernovae (SNe Ibn) are hydrogen-poor interacting explosions characterized by narrow He emission lines produced through interaction with dense circumstellar material (CSM). We present a systematic study of 40 spectroscopically classified SNe Ibn from the Zwicky Transient Facility Bright Transient Survey (ZTF/BTS). Gaussian-process fits give mean \(r\)-band half-maximum rise and decline times of \(4.9^{+1.3}_{-1.0}\) and \(8.6^{+1.8}_{-1.6}\) d, which are strongly correlated. The interacting stripped-envelope population (Ibn+Icn) evolves on significantly different timescales from normal BTS SNe Ib/Ic. The sample has a weighted-mean peak magnitude of \(M_r=-19.04\pm0.12\) mag, with an intrinsic scatter of 0.76 mag, and shows no clear correlation between peak luminosity, light-curve slope, or colour. We also construct a representative light-curve template.
We model the bolometric light curves with semi-analytic CSM-interaction+\(^{56}\)Ni models in \texttt{redback}. A static finite shell is preferred for 21/40 objects, a steady wind for 12/40, and a time-variable wind for 7/40. The median ejecta and CSM masses are \(0.58\,M_\odot\) and \(0.06\,M_\odot\), while the inferred CSM masses span nearly seven orders of magnitude and extend well beyond expectations from binary Case BB mass-transfer models, suggesting multiple pre-SN mass-loss channels. Multi-component fits to He~\textsc{i} \(\lambda5876\) separate the sample into P-Cygni and emission-dominated subclasses, with \(\sim2700\) km s\(^{-1}\) marking the boundary between narrow and broad components. Finally, we derive a local volumetric rate of \(255^{+46}_{-42}\) Gpc\(^{-3}\) yr\(^{-1}\), corresponding to \(\sim0.4\%\) of the core-collapse SN rate. Overall, SNe Ibn emerge as a substantially more diverse population than traditionally assumed.