A1 Journal article – refereed
SN 2017gci: a nearby Type I Superluminous Supernova with a bumpy tail
List of Authors: Fiore A, Chen TW, 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, Gutierrez CP, Hiramatsu D, Hosseinzadeh G, Howell DA, Kankare E, Lunnan R, Muller-Bravo TE, O' Neill D, Nicholl M, Rau A, Sollerman J, Terreran G, Valenti S, Young DR
Publisher: OXFORD UNIV PRESS
Publication year: 2021
Journal: Monthly Notices of the Royal Astronomical Society
Journal name in source: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Journal acronym: MON NOT R ASTRON SOC
Volume number: 502
Issue number: 2
Number of pages: 20
ISSN: 0035-8711
DOI: http://dx.doi.org/10.1093/mnras/staa4035
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.
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