Jerkstrand, A., Smartt, S. J., Inserra, C. ORCID: https://orcid.org/0000-0002-3968-4409, 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. and Young, D. R. 2017. Long-duration superluminous supernovae at late times. Astrophysical Journal 835 (1) , 13. 10.3847/1538-4357/835/1/13 |
Preview |
PDF
- Published Version
Download (2MB) | Preview |
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 μm, and Mg i 1.50 μm, 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 ${n}_{e}\gtrsim {10}^{8}$ cm−3. Spectral models of oxygen-zone emission are investigated to put constraints on the emitting region. Models require $M({\rm{O}} \mbox{-} \mathrm{zone})\gtrsim 10$ 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 ${M}_{\mathrm{ZAMS}}\gtrsim 40\,{M}_{\odot }$. 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 $f\lesssim 0.01$ for the O/Mg zone is needed to produce enough luminosity in Mg i] 4571, Mg i 1.504 μm, 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.
Item Type: | Article |
---|---|
Date Type: | Publication |
Status: | Published |
Schools: | Physics and Astronomy |
Publisher: | American Astronomical Society |
ISSN: | 0004-637X |
Date of First Compliant Deposit: | 23 January 2019 |
Date of Acceptance: | 28 November 2016 |
Last Modified: | 06 May 2023 04:45 |
URI: | https://orca.cardiff.ac.uk/id/eprint/118670 |
Citation Data
Cited 65 times in Scopus. View in Scopus. Powered By Scopus® Data
Actions (repository staff only)
Edit Item |