Ultraviolet Spectroscopy and TARDIS Models of the Broad-lined Type-Ic Supernova 2014ad

Abstract

Few published ultraviolet (UV) spectra exist for stripped-envelope supernovae, and none to date for broad-lined Type Ic supernovae (SN Ic-bl). These objects have extremely high ejecta velocities and are the only supernova type directly linked to gamma-ray bursts (GRBs). Here we present two epochs of HST/STIS spectra of the SN Ic-bl 2014ad, the first UV spectra for this class. We supplement this with 26 new epochs of ground-based optical spectra, augmenting a rich spectral time series. The UV spectra do not show strong features and are consistent with broadened versions of other SN Ic spectra observed in the UV. We measure Fe II 5169 Angstrom velocities and show that SN 2014ad has even higher ejecta velocities than most SNe Ic both with and without observed GRBs. We construct models of the SN 2014ad UV+optical spectra using TARDIS, a 1D Monte-Carlo radiative-transfer spectral synthesis code. The models fit the data well at multiple epochs in the optical but underestimate the flux in the UV, likely due to simplifying assumptions. We find that high densities at high velocities are needed to reproduce the spectra, with $\sim$3 M${}_{\odot }$ of material at $v>$ 22,000 km s${}^{-1}$, assuming spherical symmetry. Our nebular line fits suggest a steep density profile at low velocities. Together, these results imply a higher total ejecta mass than estimated from previous light curve analysis and expected from theory. This may be reconciled by a flattening of the density profile at low velocity and extra emission near the center of the ejecta.

26 pages, 14 figures, accepted in ApJ

References in corpus (24)

• Array Programming with NumPy
• The Supernova -- Gamma-Ray Burst Connection
• Physical Properties of Wolf-Rayet Stars
• Pre-Supernova Evolution of Massive Single and Binary Stars
• PESSTO : survey description and products from the first data release by the Public ESO Spectroscopic Survey of Transient Objects
• The Northern HIPASS catalogue - Data presentation, completeness and reliability measures
• Revisiting the Lick Observatory Supernova Search Volume-Limited Sample: Updated Classifications and Revised Stripped-Envelope Supernova Fractions
• Signatures of a jet cocoon in early spectra of a supernova associated with a $\gamma$-ray burst
• Extensive HST Ultraviolet Spectra and Multi-wavelength Observations of SN 2014J in M82 Indicate Reddening and Circumstellar Scattering by Typical Dust
• The properties of the "standard" type Ic supernova 1994I from spectral models
• Double-peaked Oxygen Lines Are not Rare in Nebular Spectra of Core-Collapse Supernovae
• Evolutionary Models for Type Ib/c Supernova Progenitors
• Ultraviolet Spectroscopy of Supernovae: The First Two Years of Swift Observations
• The Broad-Lined Type Ic SN 2012ap and the Nature of Relativistic Supernovae Lacking a Gamma-ray Burst Detection
• SN 2006aj Associated with XRF 060218 At Late Phases: Nucleosynthesis-Signature of A Neutron Star-Driven Explosion
• An ultraviolet excess in the superluminous supernova Gaia16apd reveals a powerful central engine
• Carnegie Supernova Project-II: Near-infrared Spectroscopy of Stripped-Envelope Core-Collapse Supernovae
• Ultraviolet Spectroscopy of Type IIb Supernovae: Diversity and the Impact of Circumstellar Material
• iPTF17cw: An engine-driven supernova candidate discovered independent of a gamma-ray trigger
• Early-Time Ultraviolet Spectroscopy and Optical Follow-up Observations of the Type IIP Supernova 2021yja
• Modelling of SN2013dx associated with the low-redshift GRB130702A points to diversity in GRB/SN properties
• Probabilistic Reconstruction of Type Ia Supernova SN 2002bo
• ASASSN-14lp: two possible solutions for the observed UV suppression
• Constraints on the environment and energetics of the Broad-Line Ic SN2014ad from deep radio and X-ray observations