paper

A Hydrogen-Poor Superluminous Supernova with Enhanced Iron-Group Absorption: A New Link Between SLSNe and Broad-Lined Type Ic SNe

arXiv:1810.11051 · doi:10.3847/1538-4357/aafa13

Abstract

We present optical observations of the Type I superluminous supernova (SLSN-I) SN2017dwh at , which reached mag at peak. Spectra taken a few days after peak show an unusual and strong absorption line centered near 3200Å that we identify with Co II, suggesting a high fraction of synthesized Ni in the ejecta. By month after peak, SN2017dwh became much redder than other SLSNe-I, instead strongly resembling broad-lined Type Ic supernovae (Ic-BL SNe) with clear suppression of the flux redward of Å, providing further evidence for a large mass of Fe-group elements. Late-time upper limits indicate a Ni mass of M, leaving open the possibility that SN2017dwh produced a Ni mass comparable to SN1998bw ( M). Fitting the light curve with a combined magnetar and Ni model using , we find that the light curve can easily accommodate such masses without affecting the inferred magnetar parameters. We also find that SN2017dwh occurred in the least-luminous detected host galaxy to date for a SLSN-I, with mag and an implied metallicity of . The spectral properties of SN2017dwh provide new evidence linking SLSNe-I with Type Ic-BL SNe, and in particular the high Fe-group abundance may be due to enhanced Ni production or mixing due to asphericity. Finally, we find that SN2017dwh represents the most extreme end of a correlation between continuum shape and Co II absorption strength in the near-peak spectra of SLSNe-I, indicating that Fe-group abundance likely accounts for some of the variation in their spectral shapes.

arXiv comment16 pages, 7 figures, Submitted to ApJ

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