Two stripped envelope supernovae with circumstellar interaction -- but only one really shows it

Understand

We present SN 2019tsf (ZTF19ackjszs) and SN 2019oys (ZTF19abucwzt).

• These two stripped envelope Type Ib supernovae suddenly showed a (re-)brightening in their late light curves.
• We investigate this in the context of circumstellar material (CSM) interaction with previously ejected material, a phenomenon that is unusual among SE SNe.
• We analyse observational data, consisting of optical light curves and spectra.