SN 2017gci: a nearby Type I Superluminous Supernova with a bumpy tail
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Oxford University Press
Supernovae: generalSupernovae individual: SN 2017gci
Published version: A Fiore... [et al.]. SN 2017gci: a nearby Type I Superluminous Supernova with a bumpy tail, Monthly Notices of the Royal Astronomical Society, Volume 502, Issue 2, April 2021, Pages 2120–2139, [https://doi.org/10.1093/mnras/staa4035]
SponsorshipPRIN-INAF 2017; National Science Foundation (NSF) AST1911225 AST-1813176 AST-2008108; CONICYT PFCHA/DOCTORADOBECAS CHILE/2017 72180113; Polish NCN MAESTRO 2014/14/A/ST9/00121; Alexander von Humboldt Foundation; European Commission 842471; European Commission 839090; European Commission PGC2018-095317-B-C21; VILLUM FONDEN 19054; Royal Astronomical Society Research Fellowship; Marie Sklodowska-Curie Individual Fellowship within the Horizon 2020 European Union (EU) Framework Programme for Research and Innovation H2020-MSCA-IF-2017-794467; National Science Foundation (NSF) AST-1909796 AST-1238877; University of Arizona 2018A-UAO-G16; Smithsonian Institution 2018A-UAO-G16; National Aeronautics & Space Administration (NASA) NW440 NNX08AR22G NNX12AR65G NNX14AM74G; W.M. Keck Foundation; Northwestern University; Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA); European Organisation for Astronomical Research in the Southern Hemisphere 199.D-0143 0100.D-0751(B) 0101.D-0199(B) 099.A-9025(A) 0100.A-9099(A)099.A-9099 0100.A-9099; German Research Foundation (DFG); European Commission HA 1850/28-1; National Aeronautics & Space Administration (NASA) NNX12AR55G 80NSSC19k1639; Google Summer of Code initiative; ESA's Summer of Code in Space program; European Commission 615929
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 angstrom after similar to 51 d from the maximum light, which is followed by a sharp knee in the LC. If we interpret this feature as H alpha, 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 similar or equal to 6 x 10(14) G, an initial period of the magnetar P-initial similar or equal to 2.8 ms, an ejecta mass M-ejecta similar or equal to 9M(circle dot) and an ejecta opacity kappa similar or equal to 0.08 cm(2) g(-1). A CSM-interaction scenario would imply a CSM mass similar or equal to 5 M-circle dot and an ejecta mass similar or equal to 12M(circle dot). Finally, the nebular spectrum of phase + 187 d was modeled, deriving a mass of similar or equal to 10 M-circle dot 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 M-circle dot) star.