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Nicholl, M, Berger, E, Margutti, R, Chornock, R, Blanchard, PK, Jerkstrand, A, Smartt, SJ, Arcavi, I, Challis, P, Chambers, KC, Chen, TW, Cowperthwaite, PS, Gal-Yam, A, Hosseinzadeh, G, Howell, DA, Inserra, C, Kankare, E, Magnier, EA, Maguire, K, Mazzali, PA , McCully, C, Milisavljevic, D, Smith, KW, Taubenberger, S, Valenti, S, Wainscoat, RJ, Yaron, O and Young, DR (2016) SUPERLUMINOUS SUPERNOVA SN 2015bn in the NEBULAR PHASE: EVIDENCE for the ENGINE-POWERED EXPLOSION of A STRIPPED MASSIVE STAR. ASTROPHYSICAL JOURNAL LETTERS, 828 (2). ISSN 2041-8205
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Abstract
© 2016. The American Astronomical Society. All rights reserved.We present nebular-phase imaging and spectroscopy for the hydrogen-poor superluminous supernova (SLSN) SN 2015bn, at redshift z = 0.1136, spanning +250-400 days after maximum light. The light curve exhibits a steepening in the decline rate from 1.4 mag (100 days)-1 to 1.7 mag (100 days)-1, suggestive of a significant decrease in the opacity. This change is accompanied by a transition from a blue continuum superposed with photospheric absorption lines to a nebular spectrum dominated by emission lines of oxygen, calcium, and magnesium. There are no obvious signatures of circumstellar interaction or large 56Ni mass. We show that the spectrum at +400 days is virtually identical to a number of energetic SNe Ic such as SN 1997dq, SN 2012au, and SN 1998bw, indicating similar core conditions and strengthening the link between "hypernovae"/long gamma-ray bursts and SLSNe. A single explosion mechanism may unify these events that span absolute magnitudes of -22 < M B < -17. Both the light curve and spectrum of SN 2015bn are consistent with an engine-driven explosion ejecting 7-30 M o of oxygen-dominated ejecta (for reasonable choices in temperature and opacity). A strong and relatively narrow O i λ7774 line, seen in a number of these energetic events but not in normal supernovae, may point to an inner shell that is the signature of a central engine.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | 0201 Astronomical And Space Sciences |
| Subjects: | Q Science > QB Astronomy |
| Divisions: | Astrophysics Research Institute |
| Publisher: | IOP PUBLISHING LTD |
| Date Deposited: | 13 Apr 2017 12:37 |
| Last Modified: | 04 Sep 2021 11:43 |
| DOI or ID number: | 10.3847/2041-8205/828/2/L18 |
| URI: | https://researchonline.ljmu.ac.uk/id/eprint/6258 |
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