Pre-maximum spectroscopic diversity of hydrogen-poor superluminous supernovae

Abstract

We search for the reasons behind the spectroscopic diversity of hydrogen-poor superluminous supernovae (SLSNe-I) in the pre-maximum phase. Our analysis is a continuation of the paper of \citet{ktr21}, who disclosed two new subtypes of SLSNe-I characterized by the presence/absence of a W-shaped absorption feature in their pre-maximum spectra between 4000 and 5000 Å(called Type~W and Type~15bn, respectively). However, the physical cause of this bimodality is still uncertain. Here we present pre-maximum spectral synthesis of 27 SLSNe-I with special attention to the photospheric temperature ($T_{\mathrm{phot}}$) and velocity ($v_{\mathrm{phot}}$) evolution. We find that a $T_{\mathrm{phot}}$ limit of 12000~K separates the Type~W and Type~15bn SLSNe-I: Type~W objects tend to show $T_{\mathrm{phot}}\ge$12000~K, while Type~15bn ones have $T_{\mathrm{phot}}\le$12000~K. This is consistent with the chemical composition of the studied objects. Another difference between these groups may be found in their ejecta geometry: Type W SLSNe-I may show null-polarization, implying spherical symmetry, while the polarization of Type 15bn objects may increase in time. This suggests a two-component model with a spherical outer carbon-oxygen layer and an asymmetric inner layer containing heavier ions. The two subgroups may have different light curve evolution as well, since 6 Type~W objects show early bumps, unlike Type 15bn SLSNe-I. This feature, however, needs further study, as it is based on only a few objects at present.

23 pages, 37 figures

References in corpus (19)

• SN 2005ap: A Most Brilliant Explosion
• Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies
• Superluminous supernova 2015bn in the nebular phase: evidence for the engine-powered explosion of a stripped massive star
• Spectropolarimetry of superluminous supernovae: insight into their geometry
• The host galaxy of the super-luminous SN 2010gx and limits on explosive nickel-56 production
• On the early-time excess emission in hydrogen-poor superluminous supernovae
• A Dip after the Early Emission of Super-Luminous Supernovae: A Signature of Shock Breakout within Dense Circumstellar Media
• Superluminous supernovae: an explosive decade
• Time-resolved polarimetry of the superluminous SN 2015bn with the Nordic Optical Telescope
• SN 2018bsz: a Type I superluminous supernova with aspherical circumstellar material
• Photometric, polarimetric, and spectroscopic studies of the luminous, slow-decaying Type Ib SN 2012au
• Taking stock of SLSN and LGRB host galaxy comparison using a complete sample of LGRBs
• SN 2017gci: a nearby Type I Superluminous Supernova with a bumpy tail
• Late-Phase Spectropolarimetric Observations of Superluminous Supernova SN 2017egm to Probe the Geometry of the Inner Ejecta
• SN 2018hti: a nearby superluminous supernova discovered in a metal-poor galaxy
• Photospheric Velocity Gradients and Ejecta Masses of Hydrogen-poor Superluminous Supernovae -- Proxies for Distinguishing between Fast and Slow Events
• RINGO3 polarimetry of very young ZTF supernovae
• Post maximum light and late time optical imaging polarimetry of type I superluminous supernova 2020znr
• Close, bright and boxy: the superluminous SN 2018hti

Cited by in corpus (4)

• Optical polarization and spectral properties of the H-poor superluminous supernovae SN 2021bnw and SN 2021fpl
• Exploring GRBs and supernovae connection: does a superluminous hypernova population exist?
• Dynamics and observational signatures of core-collapse supernovae with central engines: hydrodynamics simulations with Monte Carlo post-processing
• Eruptive mass loss less than a year before the explosion of superluminous supernovae: I. The cases of SN 2020xga and SN 2022xgc