Photospheric Velocity Gradients and Ejecta Masses of Hydrogen-poor Superluminous Supernovae -- Proxies for Distinguishing between Fast and Slow Events

Abstract

We present a study of 28 Type I superluminous supernovae (SLSNe) in the context of the ejecta mass and photospheric velocity. We combine photometry and spectroscopy to infer ejecta masses via the formalism of radiation diffusion equations. We show an improved method to determine the photospheric velocity by combining spectrum modeling and cross correlation techniques. We find that Type I SLSNe can be divided into two groups by their pre-maximum spectra. Members of the first group have the W-shaped absorption trough in their pre-maximum spectrum, usually identified as due to O II. This feature is absent in the spectra of supernovae in the second group, whose spectra are similar to SN~2015bn. We confirm that the pre- or near-maximum photospheric velocities correlate with the velocity gradients: faster evolving SLSNe have larger photosheric velocities around maximum. We classify the studied SLSNe into the Fast or the Slow evolving group by their estimated photosheric velocities, and find that all those objects that resemble to SN~2015bn belong to the Slow evolving class, while SLSNe showing the W-like absorption are represented in both Fast and Slow evolving groups. We estimate the ejecta masses of all objects in our sample, and obtain values in the range of 2.9 ($\pm$0.8) - 208 ($\pm$61) $M_{\odot }$, with a mean of $43(\pm 12)M_{\odot }$. We conclude that Slow evolving SLSNe tend to have higher ejecta masses compared to the Fast ones. Our ejecta mass calculations suggests that SLSNe are caused by energetic explosions of very massive stars, irrespectively of the powering mechanism of the light curve.

21 pages, Submitted to ApJ

References in corpus (19)

• PESSTO : survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects
• The magnetar model for Type I superluminous supernovae I: Bayesian analysis of the full multicolour light curve sample with MOSFiT
• SN 2005ap: A Most Brilliant Explosion
• SOUSA: the Swift Optical/Ultraviolet Supernova Archive
• The Broad-lined Type Ic SN 2003jd
• The Superluminous Transient ASASSN-15lh as a Tidal Disruption Event from a Kerr Black Hole
• Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies
• The Unique Type Ib Supernova 2005bf at Nebular Phases: A Possible Birth Event of A Strongly Magnetized Neutron Star
• Hydrogen-Poor Superluminous Supernovae from the Pan-STARRS1 Medium Deep Survey
• The hydrogen-poor superluminous supernova iPTF13ajg and its host galaxy in absorption and emission
• Superluminous supernova 2015bn in the nebular phase: evidence for the engine-powered explosion of a stripped massive star
• The host galaxy of the super-luminous SN 2010gx and limits on explosive nickel-56 production
• An ultraviolet excess in the superluminous supernova Gaia16apd reveals a powerful central engine
• The superluminous supernova SN 2017egm in the nearby galaxy NGC 3191: a metal-rich environment can support a typical SLSN evolution
• A semi-analytical light curve model and its application to type IIP supernovae
• X-rays from the location of the Bactrian Transient ASASSN-15lh
• Spatially resolved MaNGA observations of the host galaxy of superluminous supernova 2017egm
• Taking stock of SLSN and LGRB host galaxy comparison using a complete sample of LGRBs
• Spatially Resolved Molecular Gas Properties of Host Galaxy of Type I Superluminous Supernova SN 2017egm

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