LONG-DURATION SUPERLUMINOUS SUPERNOVAE AT LATE TIMES

• Published in: The Astrophysical journal 2017-01, Vol.835 (1), p.13
• Main Authors: Jerkstrand, A., Smartt, S. J., Inserra, C., Nicholl, M., Chen, T.-W., Krühler, T., Sollerman, J., Taubenberger, S., Gal-Yam, A., Kankare, E., Maguire, K., Fraser, M., Valenti, S., Sullivan, M., Cartier, R., Young, D. R.
• Format: Article
• Language: English
• Subjects: abundances; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Calcium; CARBON MONOXIDE; COMPUTERIZED SIMULATION; Constraint modelling; DENSITY; Ejecta; ELECTRON DENSITY; Emission analysis; EXPLOSIONS; GALAXIES; INSTABILITY; LSQ14an; LUMINOSITY; MAGNESIUM; MASS; Near infrared observations; nuclear reactions; nuclear reactions, nucleosynthesis, abundances; NUCLEOSYNTHESIS; OXYGEN; PULSATIONS; RADIANT HEAT TRANSFER; radiative transfer; SN 2015bn; SPECTRA; Supernovae; supernovae: general; supernovae: individual (SN 2007bi; supernovae: individual (SN 2007bi, LSQ14an, SN 2015bn); TYPE I SUPERNOVAE
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.3847/1538-4357/835/1/13

ABSTRACT Nebular-phase observations and spectral models of Type Ic superluminous supernovae (SLSNe) are presented. LSQ14an and SN 2015bn both display late-time spectra similar to galaxy-subtracted spectra of SN 2007bi, and the class shows strong similarity with broad-lined SNe Ic such as SN 1998bw. Near-infrared observations of SN 2015bn show a strong Ca ii triplet, O i 9263, O i 1.13 m, and Mg i 1.50 m, but no distinct He, Si, or S emission. The high Ca ii NIR/[Ca ii] 7291, 7323 ratio of ∼2 indicates a high electron density of cm−3. Spectral models of oxygen-zone emission are investigated to put constraints on the emitting region. Models require M to produce enough [O i] 6300, 6364 luminosity, irrespective of the powering situation and the density. The high oxygen-zone mass, supported by high estimated magnesium masses, points to explosions of massive CO cores, requiring . Collisions of pair-instability pulsations do not provide enough mass to account for the emission. [O ii] and [O iii] lines emerge naturally in many models, which strengthens the identification of broad [O ii] 7320, 7330, [O iii] 4363, and [O iii] 4959, 5007 in some spectra. A small filling factor for the O/Mg zone is needed to produce enough luminosity in Mg i] 4571, Mg i 1.504 m, and O i recombination lines, which shows that the ejecta is clumped. We review the constraints from the nebular spectral modeling in the context of the various scenarios proposed for SLSNe.