SN 2017gci: a nearby Type I Superluminous Supernova with a bumpy tail. Issue 2 (5th January 2021)

• Record Type: Journal Article
• Authors: Fiore, A; Chen, T-W; Jerkstrand, A; Benetti, S; Ciolfi, R; Inserra, C; Cappellaro, E; Pastorello, A; Leloudas, G; Schulze, S; Berton, M; Burke, J; McCully, C; Fong, W; Galbany, L; Gromadzki, M; Gutiérrez, C P; Hiramatsu, D; Hosseinzadeh, G; Howell, D A; Kankare, E; Lunnan, R; Müller-Bravo, T E; O' Neill, D; Nicholl, M; Rau, A; Sollerman, J; Terreran, G; Valenti, S; Young, D R
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 502:Issue 2(2021)
• Page Start: 2120
• Page End: 2139
• Publication Date: 2021-01-05
• Subjects: Transients: supernovae -- supernova: general -- supernovae: individual: SN 2017gci; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa4035
• Languages: English
• ISSNs: 0035-8711

Abstract

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 M g = −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 H α, 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 B p ≃ 6 × 10 14 G, an initial period of the magnetar P initial ≃ 2.8 ms, an ejecta mass $M_{\rm ejecta}\simeq 9\, \mathrm{M}_\odot $ and an ejecta opacity $\kappa \simeq 0.08\, \mathrm{cm}^{2}\, \rm{g}^{-1}$ . A CSM-interaction scenario would imply a CSM mass $\simeq 5\, \mathrm{M}_\odot $ and an ejecta mass $\simeq 12\, \mathrm{M}_\odot $ . Finally, the nebular spectrum of phase + 187 d was modeled, deriving a mass of $\sim 10\, {\rm M}_\odot$ 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 ($40\, {\rm M}_\odot$ ) star.