SN 2015bn: A DETAILED MULTI-WAVELENGTH VIEW OF A NEARBY SUPERLUMINOUS SUPERNOVA
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Nicholl-2016-SN 2015bn_ A DETAILE.pdf
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Author(s)
Nicholl, M.
Berger, E.
Smartt, S. J.
Margutti, R.
Kamble, A.
Alexander, K. D.
Chen, T.-W.
Inserra, C.
Arcavi, I.
Blanchard, P. K.
Date Issued
July 2016
Journal
Astrophysical Journal
Publisher
IOP Publishing
Citation
Nicholl, M., E. Berger, S. J. Smartt, R. Margutti, A. Kamble, K. D. Alexander, T.-W. Chen, et al. “SN 2015bn: A DETAILED MULTI-WAVELENGTH VIEW OF A NEARBY SUPERLUMINOUS SUPERNOVA.” The Astrophysical Journal vol. 826, no. 1, 39, July 2016, pp. 1-31. © 2016 The American Astronomical Society.
Version
Final published version
Abstract
We present observations of SN 2015bn (=PS15ae = CSS141223-113342+004332 = MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at redshift z = 0.1136. As well as being one of the closest SLSNe I yet discovered, it is intrinsically brighter (M[subscript U] ≈ -23.1) and in a fainter galaxy (M[subscript B] ≈ -16.0) than other SLSNe at z ∼ 0.1. We used this opportunity to collect the most extensive data set for any SLSN I to date, including densely sampled spectroscopy and photometry, from the UV to the NIR, spanning −50 to +250 days from optical maximum. SN 2015bn fades slowly, but exhibits surprising undulations in the light curve on a timescale of 30–50 days, especially in the UV. The spectrum shows extraordinarily slow evolution except for a rapid transformation between +7 and +20–30 days. No narrow emission lines from slow-moving material are observed at any phase. We derive physical properties including the bolometric luminosity, and find slow velocity evolution and non-monotonic temperature and radial evolution. A deep radio limit rules out a healthy off-axis gamma-ray burst, and places constraints on the pre-explosion mass loss. The data can be consistently explained by a ≳ 10 M [subscript ⊙] stripped progenitor exploding with ∼10 [superscript 51] erg kinetic energy, forming a magnetar with a spin-down timescale of ~20 days (thus avoiding a gamma-ray burst) that reheats the ejecta and drives ionization fronts. The most likely alternative scenario—interaction with ~20 M [subscript ⊙] of dense, inhomogeneous circumstellar material—can be tested with continuing radio follow-up.
MIT Department
MIT Kavli Institute for Astrophysics and Space Research
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DOI of Published Version
https://doi.org/10.3847/0004-637x/826/1/39
