Dramatic rebrightening of the type-changing stripped-envelope supernova SN 2023aew

Kavli Affiliate: Michael Fausnaugh

| First 5 Authors: Yashvi Sharma, Jesper Sollerman, Shrinivas R. Kulkarni, Takashi J. Moriya, Steve Schulze

| Summary:

Multi-peaked supernovae with precursors, dramatic light-curve rebrightenings,
and spectral transformation are rare, but are being discovered in increasing
numbers by modern night-sky transient surveys like the Zwicky Transient
Facility (ZTF). Here, we present the observations and analysis of SN 2023aew,
which showed a dramatic increase in brightness following an initial luminous
(-17.4 mag) and long (~100 days) unusual first peak (possibly precursor). SN
2023aew was classified as a Type IIb supernova during the first peak but
changed its type to resemble a stripped-envelope supernova (SESN) after the
marked rebrightening. We present comparisons of SN 2023aew’s spectral evolution
with SESN subtypes and argue that it is similar to SNe Ibc during its main
peak. P-Cygni Balmer lines are present during the first peak, but vanish during
the second peak’s photospheric phase, before H$alpha$ resurfaces again during
the nebular phase. The nebular lines ([O I], [Ca II], Mg I], H$alpha$) exhibit
a double-peaked structure which hints towards a clumpy or non-spherical ejecta.
We analyze the second peak in the light curve of SN 2023aew and find it to be
broader than normal SESNe as well as requiring a very high $^{56}$Ni mass to
power the peak luminosity. We discuss the possible origins of SN 2023aew
including an eruption scenario where a part of the envelope is ejected during
the first peak which also powers the second peak of the light curve through
SN-CSM interaction.

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