SN 2017gci: a nearby Type I Superluminous Supernova with a bumpy tail
Date Issued
2021
Author(s)
Fiore, A.
•
Chen, T. -W.
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Jerkstrand, A.
•
•
•
Inserra, C.
•
•
•
Leloudas, G.
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Schulze, S.
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Berton, M.
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Burke, J.
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McCully, C.
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Fong, W.
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Galbany, L.
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Gromadzki, M.
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Gutiérrez, C. P.
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Hiramatsu, D.
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Hosseinzadeh, G.
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Howell, D. A.
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Kankare, E.
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Lunnan, R.
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Müller-Bravo, T. E.
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O'Neill, D.
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Nicholl, M.
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Rau, A.
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Sollerman, J.
•
Terreran, G.
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Valenti, S.
•
Young, D. R.
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 $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.
Volume
502
Issue
2
Start page
2120
Issn Identifier
0035-8711
Ads BibCode
2021MNRAS.502.2120F
Rights
open.access
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