Abstract
We present and discuss the optical spectrophotometric observations of the nearby (z = 0.087) Type I superluminous supernova (SLSN I) SN 2017gci, whose peak K-corrected absolute magnitude reaches Mg =
−21.5 mag. Its photometric and spectroscopic evolution includes
features of both slow- and of fast-evolving SLSN I, thus favoring a
continuum distribution between the two SLSN-I subclasses. In particular,
similarly to other SLSNe I, the multiband light curves (LCs) of SN
2017gci show two re-brightenings at about 103 and 142 d after the
maximum light. Interestingly, this broadly agrees with a broad emission
feature emerging around 6520 Å after ∼51 d from the maximum light, which
is followed by a sharp knee in the LC. If we interpret this feature as Hα,
this could support the fact that the bumps are the signature of late
interactions of the ejecta with a (hydrogen-rich) circumstellar
material. Then we fitted magnetar- and CSM-interaction-powered synthetic
LCs on to the bolometric one of SN 2017gci. In the magnetar case, the
fit suggests a polar magnetic field Bp ≃ 6 × 1014 G, an initial period of the magnetar Pinitial ≃ 2.8 ms, an ejecta mass Mejecta≃9M⊙ and an ejecta opacity κ≃0.08cm2g−1. A CSM-interaction scenario would imply a CSM mass ≃5M⊙ and an ejecta mass ≃12M⊙. Finally, the nebular spectrum of phase + 187 d was modeled, deriving a mass of ∼10M⊙
for the ejecta. Our models suggest that either a magnetar or CSM
interaction might be the power sources for SN 2017gci and that its
progenitor was a massive (40M⊙) star.
Original language | English |
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Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 502 |
Issue number | 2 |
Pages (from-to) | 2120–2139 |
ISSN | 0035-8711 |
DOIs | |
Publication status | Published - 2021 |
Keywords
- Transients: supernovae
- Supernova: general
- Supernovae: individual: SN 2017gci